*I go for cultural victories when playing the Krynn*
With the Krynn, I like to save a few spies (usually 3-4) early in the game and not place them anywhere. When I first start to build them I only put enough resources into it where the spy will take 50 or so turns to build. This way I didn't spend a lot of money per turn and by time the middle game comes around I have 3-4 waiting to be used.
When I see a planet around that looks like it might 'flip' with a little help I fast build 2-3 more spies. (by this time I'm making enough money per turn do do so). I then place ALL 6 or so spies on the planet. I place them on any influence buildings and FARMS if any are there. FARMS = population = influence. The comp will usually kill half of your spies but you will still have the core 3 you built early. By that time the plante has usually 'flipped' for the price of about 600-900bc for the spy fast build. This has worked for me roughly 70% of the time. When you see another worthy planet. rinse and repeat!
The key is to build those core spies early. Only put like 3-5bc into it so the spies take 50 or more turns to build. Try it out! I've done this and flipped planets within a couple of turns.

Thanks. that is what I was looking for. Much appreciated.

unfortunately, the costs of spies goes up 10 bc for each next spy, and jumps up after each 4th spy (5th spy is around 250 cash, 9th is 500 i think, 13th is 750, 17th is around 1250, 21st is some 2500 etc. 29th spy should be around 5500 or so), meaning that spy-spam tactics wont work on small maps at all, and even on larger maps could take huge amount of cash you could divert to something else.

personally i use spies for 3 reasons: to get low level espionage for every other player, so i can see what bonuses they have and my influence effect on their planets; and to weaken their defenses before invading planets (taking out farms and morale buildings), and last i use spies to block super-projects and gal. wonders.

Ok. I went ingame to verify spy stuff. I went to place some spies on the Thalan and they had 2 Galactic achievements. It would let me place a spy the Economic Direction Unit but NOT the Hyperion Matrix. It was greyed out so there wasn't even an option to do so. Any thoughts to why this is? Is the HM a race specific achievement?

"spy-spam tactics wont work on small maps at all, and even on larger maps could take huge amount of cash you could divert to something else."

The OP was talking about playing on the larger maps, and the number of spies that I recommended reflected that. On small maps it only takes a handful of spies to achieve the same result.

By the time you get to that 29th spy, at 5500bc, per your example, you can easily be bringing in over 10000bc per turn. I know that some players can generate ~50000bc per turn, so this is really just a drop in the bucket in a robust economy.

Sure you can spend your money elsewhere. You can spend your bc building up fleets of dreadnaughts, and blitzkreig your way across the galaxy. This is just another way to play a game.

There are some things that you are not allowed to place a spy on, notably the things that Rhedd_V mentioned. I don't know about the hyperion matrix. I have never tried to place a spy on one. I assumed that you could. I'll have to check that one out in-game.

I just finished a game using the Terrans where the Altarians pulled off some perfect storm colony rush. Basically, everyone in the universe (medium) had no more than 4 planets, while the Altarians had about 12. It didn't look good, as they got their military machine churning pretty quickly and started wars while most of us plebs were still researching the wheel.

Long story short, it was spies that saved me and in the end won me the game. I didn't give myself a hope in hell at first and started stocking them up as I usually do but here's the thing...

The AI's all threw every spy they had at the Altarians and by the time I remembered mine, I had about ten, which I dropped all over Altarian space. By mid-game, the lumbering light-blue giant was utterly infested with the darn things. I was scooping the cream off their research with steals, as well as completely stuffing their economy. By the time my small army of agents was done... the light blue blob was no more.

The next game I played, was my first with the Krynn.
Loving it.

indeed 10k bc bruto profit is very much achievable, playing large maps and with say 100-200 planets under control; however following same logic if playing with even remotely competitive AI opponents having say 100+ planets, the maximum damage 30 spies can inflict upon that kind of vast economy is pretty much nonexistent, maybe even contra-productive considering how easily AI can take out a spy one spent a small fortune to train..

however, i too have noticed sometimes that AI like to gang up on one particular player with spies, and in that case the spy spamming is awesome, for simple reasons: the AI has already spent all of his spies killing off foreign agents, leaving you with no danger for your spies that can easily do whatever they wish inside AI's empire, and also even if AI trains agent to null opponents agent, there is a chance that his target won't be your spy. those things considered i did on more than one occasion see opponent going from say 2nd place by total score to 6th or 7th in a mater of half-year.

oh, and i think my calculations about spy costs for more expensive spies are off, especially for those after 20th spy; i think that 30th spy would be between 3k and 4k, not 5.5k...

Yeah, I have done some of my own "research" in game as it were. I have gotten pretty good at including Espionage into my economy. It isn't really very hard provided you start out (round one) with putting money aside. More or less you don't miss what you never see. And you can usually bang out 5 or so spies before you know it. Then, you simply tailor your espionage expense based on what you have available. If you can only afford a small amount of BC every week, you still get spies that grow.

However, while I agree that there are some things that you can achieve via Espionage, I find that "As a Winning Strategy" it just lacks something (for me). Sure you can steal the occasional tech and I have seen people post strategies on how to wreck economies. I have even seen some tips on placing spies on farms or Moral facilities as a prelude to invasions. And when I am in the money, I find that I am tempted to sock huge amounts of money into Espionage. And I wonder if I am doing myself a disservice where I would be much better off simply banking the money, or force upgrading ships/facilities instead. The bottom line is that I still I find that the net gain doesn't match the cost.

When compared to other winning game strategies, by which I mean military/diplomatic, the net gain is very small for the considerable cost (IMHO). For instance, once my empire gets going, I can dedicate any number of planets to mass producing any ships my tech is capable of. By mid to late game I can pump out a fleet every other turn easily. Now, said fleet, depending on my tech and capabilities vs. my opponents, can/will take out any number of opponents ships. It can also lead to the downfall of planets or to pave the way for Terror Stars. I can block incoming invasions, or simply intimidate the Galaxy at large into giving me what I want.

Likewise, I can use Diplomacy and Influence Star bases to flip planets to my way of thinking. This is usually an investment of some money and some construction ships. It may take time, but the net is that, with 2000 BC and 8-10 construction ships (which I can have mass produced on any number of planets) and about 10 weeks, I can flip several planets to my empire.

In comparison, I find that, even when I am pumping 900 BC per week into creating spies, it can still take 10-20 (9-18,000 BC) weeks for a single spy. Now, with that spy, I can take down income on a single enemy planet by as much as 25%. Assuming a large galaxy and an empire of 15 or more planets, is more or less a drop in the bucket. I can also (occasionally) steal techs, but then invasion gives me the same and on a more consistent basis. I can, or so I am told, take out a farm or a moral facility on a planet where I am about to invade, and thus facilitate my invasion strategy. I have had varing degrees of success with these strategies so I my opinion is that they are of dubious benefit. And usually, about the time I would use them, I can usually accomplish the same thing with Tidal waves or Mini-soldiers at the cost of 500 BC or less (not 90,000 BC). And all of these strategies assume that my spy doesn't get taken out one turn after it gets placed.

Additionally I have found that most of the AI's I play against (on Challenging or Tough) usually either have a couple of 10-12 spies just stock piled up (in addition to the ones infesting MY empire), or can manufacture them all within a couple of weeks. The net is that, even if I start out with 25 spies placed throughout their empire, they all get taken out within about 10 weeks.

And then there are the Techs that are supposed to improve Espionage. What does the +25% to Espionage do exactly? Does this make them cheaper to produce? Certainly I have not noticed a significant downturn in cost. Does it make them harder to spot? Again, not that is in evidence (from my testing). And it certainly doesn’t make them harder to remove. Maybe they increase the chance to steal tecs? This (IMHO) is hardly worth the investment.

I don't mean to whine. I think that Gal Civ 2 is an AWESOME game, 10 out of 10 in my book. But I would like some improvements to this one aspect and would like ideas from the forums on what you guys think/ would like to see. Personally, I think that perhaps creating a tile training facility (along the lines of current Star Ports) would be a good start. So that if I wanted to Mass produce (I don't say spam) a Spy network, that I could generate several in a short period of weeks, not Years as is now. I am not sure about the game mechanics here, but maybe, with the inclusion of a spy facility you could then have the choice to select “spy” in the ship building que. And they could be variably expensive based on tech levels or techs researched. Even if they were hideously expensive (to prevent SPAMMING) at least, if I were of a mind to use this as my main strategy, I could devote my entire economy to this. These spies might work in a similar way to they do now (placing them on individual tiles on individual planets) but would be variably more difficult to detect/remove based on tech and espionage levels of the two races involved. Something along the idea that, I have a % chance to detect a spy after placement. And then a % chance to remove it based on placing my own spy, not the automatic that it is today. And maybe, if My espionage were high enough, I could take out THEIR spy? Or at least the spy could escape to be placed elsewhere.

I would also like to see the ability to fund a “Network of spies” in a given civilization. I am not sure how this would work, but maybe something along the lines of the old way of doing things where you could select X cash per week to go into a spy network for a given civilization. Maybe if the benefit were muted a bit over what it was, this would still be a viable (and not over-powered) strategy? Something like, you can see planets and review specs on ships, but not steal tech (or maybe only a VERY SMALL percent chance to steal tecs). Also, maybe the greater your network, the more you have visibility of ships in motion? Maybe you even get a pop-up stating “Your spy network has detected that the Drengin’s are planning to send a fleet of ships against you at Hoth V. You might want to be prepared.” That gets sent out the week before they launch? Make the benefits subtle but pervasive. And maybe you could even, once you were spending enough, covertly divert research points from the Civilization to your own?

Finally, I would like to see something that could conceivably make Espionage a Game winning strategy. There is a super ability of “Super Spy” after all. So there should be a way to win just using that. Maybe there could be an additional Invasion option that appears if your espionage is high enough with a certain Civilization, or if you have a spy (or more than one) planted on the planet you are invading? Something like, “Sacrifice your spy and $X BC for +200% Soldier Advantage”. Or maybe, once your espionage got to a certain level, you could funnel a percentage of the other Civ’s economy and research points into your empire. Or even that you could pull a “Jagged Knife” on opponents and, once you were firmly entrenched in a planet (or planets), flip the worlds without invasion. This last obviously would have to be well thought out and planned and require something like every facility on planet to be infiltrated, or with some economic price tag? Or even something wherein, once you have 5 or more spies in place for more than 10 weeks, there is a chance to flip the planet (like the influence star base strategy) something like that?

What other ideas do you guys have? I see that the great folks at Star Dock are working on Espionage tweaks now so maybe they can give us any thoughts on if any of our ideas are close to what they are thinking?