Once you research Battleships, they should make up the bulk of your armada (kinetic artillery/giga cannons), and the other ships should primarily be used to screen incoming fire. I personally use torpedo corvettes, with point defense covered destroyers, and torpedo cruisers. Why do I use cruisers with torpedoes? Because the simple fact is that they won't get off more than a few shots before being completely eradicated, best to get off most damage as possible as quickly as possible. Versus heavy shield focused compositions the energy-based torpedoes are not interceptable (to my knowledge) and deal massive shield damage. Against no-fighter, no-point defense compositions the regular torpedoes can be very efficient against shield comps.