Advent is (relatively speaking) poor at splitting up its fleet. You get a lot of benefit by having all your special abilities in play in one place. On the other hand, TEC can split up a little more easily without losing much of their luster, and Vasari can pretty much do this with impunity.
Usually an Advent player will try to provoke one big battle to decide it all. When fighting against Advent, your best course of action is to try to break him up and fight him in multiple places at once. On the opposite spectrum, a good Vasari player is going to try to split up your forces and then take cheap shots at you, trying to hit you where you're weakest. However, that's not to say that I haven't seen (or successfully played as) an Advent who splits his forces into multiple groups or a Vasari who builds a victory fleet and creams his opponent. It all depends on what the map has given you and what your approach is.
(and emphasize early trade for tec and culture for advent)
Believe it or not, no. You need a strong economy already built-up to start investing in these kinds of structures (although occasionally fast-culture can be a good choice), so really the bottom line for trade and culture isn't labs, but rather a reasonable fledgling empire that's already been built. Before the buff to the Akkan capital ship (which improved TEC's colonization ability) often it was Advent that had trade ports on the field first because they could expand cheaper and faster in the early game.