Advent fleets and what to do with them

Has anyone explicitly said only keep one fleet? While it's true the advent work best in as large of groups as possible as many of thier units and abilities help the others, ultimately you need to have enough fleets to prevent your enemies from attacking your core worlds. Ideally you will have two fleets, one for attacking, another for defending. However, wide open maps or allies in trouble might force you to have more than this. Perhaps their defenses might be good enough to not have a defending fleet in entrenchment, but I'd still leave a small fleet around your homeworld and economic powerhouses, especially if you're playing vasari. Just use common sense when deciding how many groups you need to split your fleet into, but don't make any more than you have to.

if its late game, try to at least have a full set of ships (one of each) per fleet. Advent rely heavily on abilities.

The heavy reliance on abilities is one reason Advent is so nerfed compared to other civs.   It is nearly impossible to get the right abilities running at the right time in the ideal situation they demand, and the individual abilities mostly seem far less useful than similar ones in other civs.   One bad map position, for example, can completely destroy Advent's ability to get certain research which then dooms them to quick destruction.   Unless you are playing against new players, Advent is not for the inexperienced.   

Other civs abilities and general economy are far better and can support a whole lot more waste.  Advent is gimped, so you need to be a good player to play them successfully.

Advent has a clear advantage in huge single-fleet battles, while Vasari has a clear advantage in small-scale skirmishes.  TEC comes somewhere down the middle.  This doesn't mean that Vasari can (or even should) avoid huge fleet battles or that Advent can avoid multiple fronts.  It just means they excel under different situations.  Always evaluate the situation based on your current economic and military position.  If you've got a map where you'll have to spend five minutes to run from one side of your empire to another, keeping a single big fleet just isn't practical.

Advent is a tricky faction to play, but I wouldn't say they're "gimped".  Their economic upgrades are weaker, but on the flip-side the savings a mothership will give you on your planetary upgrades are enough to mitigate those issues well into the mid-game.  As I said in an earlier thread, Advent really aren't at a civic tech disadvantage until the other races start putting up four or five labs.  By that point in the game, Advent can be putting up four or five military labs, and unlock some of their exceptionally dangerous units and techs like repulsion.  Obviously Advent has to be far more aggressive into the mid-game, but they're well equipped for that.

its still a huge problem that there's nothing an Advent player can get that competes on the same level as Returning Armada (or even a phase node network without RA) or Pervasive Economy. the end-game disadvantage of the Advent civil tech tree is a big issue in the game balance right now. its designed to overwhelm with culture and flip planets more easily, but culture is pretty weak in this game compared to military or just credit economy.