I've used some of the Advanced Fleet ground weapons, not bad. Bought a AP Pulsewave, Spilt Beam, and High Density Beam. Avoided the Elite stuff because you could only get Phaser, and really wanted the AP proc over the Phaser one.
Honestly, don't use them much anymore. Everything's too specific to who you are fighting. Had a bunch with BORG procs, but don't do that much anymore. Now the Voth proton stuff is the way to go for the Battlezone, so I go that direction (got the T5 Rep stuff). The High density and Split Beam rifles are the most useful, I guess, as they'd be good general purpose weapons for a BOFF to use.
My backup kit is still the Adapted MACO (basically Honor Guard set for Fed players), I like the disruptor pulsewave plus grenade launcher, and keep that as my secondary gun. Good for crowd control.
Really depends on where you plan to play.
Every time they release more sets, I start to have more trouble storing things, though. Sucks to throw away those hard-earned sets, but only so much storage and despite releasing more and more 3 and 4 piece sets, the storage hasn't increased to PUT them anywhere. Like the 15 special tribbles or non-combat pets. Where do you store them after a while? And can't get them again, sucks to just throw them away...