It depends what stage of the game you're in.

Early on, I think most do a Kol as their first cap with some light frigs, while trying to get LRMs as soon as possible. Probably have some flak mixed in there too.

Late game, LRMs can be useful but they aren't as dominate. Assuming it's very late game with fleet sizes near their max, my fleet usually looks something like this:

6 or so caps in total - 3 kols, 2 donavs (sp?), 1 or 2 planet bombarders (forgot their nammes). You also want lots of heavy cruisers and a good number of repair cruisers - a couple of command cruisers are nice too. Once you research the light frigs ability, they are a helpful counter to advent. LRMs and flak are also useful.

Basically, I find that balance is important in a large fleet. If you're opponent is just spamming the same stuff again and again, consider making more of their counter. Typically, unless its early game and im using lots of LRMs, I try to have a balance fleet overall.

By the late game, I tend to have lots of LRMs and a small cadre of heavy cruisers as the main portions of my fleet. The heavy cruisers go in and soak up some fire while the LRMs lay down heavy fire from afar. I also like to have lots of robotics cruisers with demolition bots upgrade. Demo bots disable an enemy ships weapons for pretty good period of time (it's either 45 seconds or 60 seconds, can't remember offhand which). Since they're cheaper than heavy cruisers, you can get a lot of them and keep a big percentage of the other guy's fleet disabled. Also, their repair bots can keep your fleet repaired and fighting hard. I also use the command cruiser, but in much small numbers. Don't need as many. Their researchable upgrade, Designate Target, is good for taking down enemy capitals quick.

As for capital ships, there are several options. Two Dunovs in concert can work well. They can use the shield recharge ability on each other, and also EMP charge to remove the anti matter of enemy support ships is a seriously underrated ability. Since Advent and Vasari have strong support cruisers and strong capital ship abilities, at least one Dunov can be a priceless asset to a TEC player. Another good capital combination is Kol / Dunov / Sova. The Kol gives you staying power in combat, the Dunov is good for reasons already listed, and getting a Sova filled completely up with interceptors will do two things: it keeps the enemy bombers at bay and gives you a highly mobile force of strikecraft that can do some serious damage to enemy LRFs. You can also substitute a Marza for the Kol if you like the Marza's abilities better. If you do that, you'll need to concentrate more on heavy cruisers so you'll have ships with staying power.