I play on Elite, starting with Bravo Sector, and find that the optimal upgrade path goes roughly like this:
-Air to Air Missiles (a pickup, sell for Auto-Tracking Minigun)
-Air to Ground Missiles (a pickup, probably sell for Auto-Tracking Minigun)
-Dumbfire Missiles (a pickup, sell immediately since you should have the Minigun already)
The strategy in Bravo Sector is to get the Auto-Tracking Minigun ASAP, at least for an optimal run. It's just that powerful (and profitable). In fact, I rather dislike it because of how it overshadows all other pre-laser weapons. The Air-to-Ground Missiles can serve a niche role, but that's about it.
-Laser Turret (selling Auto-Tracking Minigun)
The Auto-Tracking Minigun quickly becomes too weak for Tango Sector, but the Laser Turret is almost as good in Tango as the Minigun was in Bravo. Sell off additional weapon pickups in order to save for a Deathray. If you've done really well, it might even be feasible to skip the Deathray and go straight for the Twin Laser - which you'll need in the Outer Reaches, as enemies get too durable for the Laser Turret to handle.
-Twinlaser (selling Deathray and/or Laser Turret)
It's all about raw firepower when you get this far. The turrets just don't have the oomph to rack up regular kills, and most of the bosses are ground targets unreachable by the Laser Turret. If you accumulate enough cash, you could even abuse weapon switching to run a Twinlaser/Deathray combo for maximum killing power.
Remember that, in all three sectors, you only want to buy the absolute minimum amount of energy and phase shields you can get away with. Weapons are what give you return on your investment. Buying a bunch of shields before you absolutely need them is a big loss in the long run.
Note, however, that just because this is the optimal path doesn't necessarily make it the most fun. Experimenting with funky builds (rush to Dumbfires!) can be a big part of the fun.
Post edited August 25, 2010 by Corbeau