This game is NOT about trade.
Having said that you will need to form colonies and set up trade gates if you want to try and create a dominion in the heavens.
The only restriction on your fleet size is the 'fleet support' you have available. This value is a basic of 40 when you join and is increased when you establish colonies. A colony provides fleet support equal to it's population minus Nova shuttle tax. The fleet support from a colony is a simple abstraction of the real trading and commerce that a colony takes part in.
All races have a fleet support value of 40, and can never have less that that. This means, even if you never form any colonies you can still field a formidable fleet and enjoy combat. This is actually a very good way to play for those with time pressure in real life.
If you move one of your vessels within 5 hexes of an enemy trade gate then your ship gains control of the gate and all goods are boosted to your own races nova shuttles. Your ship has to be the only vessel within 5 hexes. If more than 1 race has a ship within 5 hexes of the trade gate then it stops functioning. Again, players with no colonies of their own can focus on piracy for short term gains in their fleet support level - short as the enemy will no doubt fight to regain control.
If a system is within 4 RipCurrents of your homeworld then placing a Trade Gate construct in the system will cause compatible planets to automatically get colonised. These colonies grow at 1 per galactic turn to their maximum. Loss of the gate will cause them to shrink.
Colonies contribute goods equal to their population, these goods minus any Nova Tax count towards your fleet support. Nova shuttles from your homeworld carry the colonists and goods - they are not part of the game.
The fleet support is the maximum fleet size that you can have. Each ship class costs a different amount (as shown here). If your current fleet exceeds your fleet support level then you cannot build any new ships.
The Nova shuttle clans charge hefty tax rates for transporting your goods. The tax rates depend entirely on the number of RipCurrent legs between the system and the nearest trade hub. Initially, your only trade hub will be your homeworld. The amount after tax goes towards your races total fleet support value. This is only calculated on a galactic turn.
It is worth mentioning that if you place a trade gate in an open system (one with 10 planets or more), the system counts as only 2 legs from your homeworld, and you can settle new systems connected by current to that system. Open systems are worth fighting for.
Construction drones can only deploy 20 hexes from the nearest planet. A construction drone punctures the exotic barrier between real space and rip space. Once this has been done, providing there are compatable planets, and that the system is within 4 legs of your homeworld then the planets will start to get settlers.