Honestly if you just rush both Trade and Interstellar Republics, your diplomacy skill will be such that races you don't really even talk to will just melt in your arms.

First rule: Don't trade away diplomatic techs. Obviously, you want to maximize the diplomacy gap between you and the other civs to increase the value of your trades; why would you damage this advantage?

Second: Try to acquire at least one trade and/or economic treaty early on from each civ. Not only will the long run benefits of these treaties greatly outweigh whatever you traded to get them, but establishing the treaty itself will make those civs less inclined to attack you, as they would take a permanent hit on their own diplomacy from breaking a treaty, and they don't like that.

Third rule: make sure you trade any given tech to everyone; you don't want to lose any deals by allowing civs to trade between themselves. On the same principle: immediately destroy any new minor civ that emerges. Since you are likely to be the leader in technology, any emergent civ will start with ALL your techs; don't give them a chance to trade away all your valuables.

Fourth rule: When trying to incite war, look particularly for a weak civ with stronger allies, then get the civ with the highest military (and preferably one who hates them) and bribe them to attack. Because they only evaluate the target civ's military, and not their allied military, it should be relatively cheap, and then all the involved civs will become embroiled in war. These civs will devote many resources to the war, giving you an opportunity to surge ahead. You may want to consider trading Alliances away to seed alliances between the other civs; yes this goes against rule #1, but depending on the circumstances, draining other civs of resources may outweigh a small boost of your own.

thanks Millertime and Iztok. I'm looking forward to the challenge that this is going to provide for me. I am willing to let myself fail, as long as I learn something and can come back and win it later.

And micromanagement is ok, I don't mind

I think you'll see rather quickly how powerful your "trades" will become. Super Diplomat, if you have the patience and time to do all the trading is insanely powerful. As for tips on the trading screen, if you're REALLY picky, just remember to round off any trade you make with cash from the AI.

Also, dont underestimate the power of trading for warships. Not only does it increase your military, it obviously decreases the AI's AND you have immediate ships in enemy (or future enemy) territory. End game this might be a little more difficult since your playing a gigantic map, since 6 or 7 warships might be peanuts compared to the thousands flying around. Trading for the AI's troop transports is also fun...

I've had alliances broken due to the assassination event, but I don't recall any other instance. This happens regardless of espionage level, though higher espionage does seem to reduce the chance of it occurring. This also, if I remember correctly, happens regardless of mega events-i.e., it's not actually a mega event. I could be wrong on that, though.

However, I have yet to see this event populate the galaxy with anything other than Vengeance-class ships, which tend to have either 2 or 3 attack and no defense on, if I remember correctly, a tiny hull. It also apparently switches all of that AI's starports to production of the Vengeance model, which can have up to 1 more attack than the spawned ones, but are extremely weak regardless.

As a note, the Vengeance's stats do not change regardless of the AI's or your tech level, at last check; though, I can't remember it happening for some time now.