I always fill up my colony ships. It helps the colony to become productive (in terms of income) if it starts from a larger base population.

The tech tree question is a lot harder to answer, as it depends on what size galaxy you're playing, whether there are a lot of habitable planets, etc. There are some interesting posts in the strategy forums on this.

The colonists you put on the ship are subtracted from the population of the home world, so you don't want to do this on a world with a low population.

Way to make an ass of yourself twice in the same post - by flaming a newb and quoting the wrong post while doing so.

Also, while colonising, you may want to NOT build anything on the new planets for a while.

New colonies cost enough without the added costs for production and maintenance.

You get a population of zero, IIRC. It will still grow, but very slowly. Yes, you get to colonize the planet, but you face steep econonomic losses until that planet gets a population - and starting from zero, it could be half a game year or more before you break even.

The same thing happens when you spore a planet.

You'll note I didn't say this wasn't worthwhile in some specific circumstances, it's just not generally economically viable. If nothing else, follow up your converted "colony ship" with a real one (or a transport if you have them) and leave it parked in orbit for a few turns. After 5-6 turns send it on it's way, and the population that grew while it was there will give your planet a healthy boost.

This works especially well if there is a good planet nearby you need tech to get. Park your colony ship until you finish researching what you need instead of just waiting.

Not without researching the first two or three levels of miniaturization. Small hulls work, and are still cheaper than cargo hulls.

I'm still playing DA (long story) but I generally have two standard colony designs - one based on a cargo hull, and one on a small hull.

The small hull has nothing but a colony module, making them fast and cheap to spam. These are excellent for short distances or colonies that don't have much capacity to build yet.

The cargo hull has the colony module, life support, and as many engines as I can cram on it. This is good for settling planets further from your center, or starting a cluster of colonies. Send one out, let it grow a few turns while buildings are set up, then start launching small colony ships from it. These ships also get built by colonies that have factory bonuses, to slow down production to where the population can replace what's lost with each new ship.

The important part is: build both of these with starting tech. Both designs are available to me from turn one, and rarely do I need to upgrade the designs during a game.