If you want to fight, you can update to the Eagle right now with your funds. Aim at the Viper, which is the best fighting vessel early on. However, both Eagle and Viper can't do much else than combat and running missions.
The Cobra, as suggested by many here, is an excellent ship, but requires a lot more money to equip. I remember I bought the Cobra as soon as I could afford the hull (plus insurance, always keep some money left over for insurance!), and I quickly sold it again because I noticed I couldn't afford any upgrades. All new ships come with E grade equipment, which is very poor. So you need some more cash available for a new ship, not only the hull. I went Sidewinder -> Eagle (->Cobra, fail) -> Viper and then Cobra again. I used both Viper and Cobra for a very long time and still love both. Remember you can own multiple ships, so when you have the money later, nothing stops you to buy back that one ship you loved so much earlier on even though it's not "the best" in addition to your current ship(s).
About gimballed, that's a matter of hot debate. Fixed weapons do more damage, but are more difficult to aim with. Gimballed weapons do a bit less damage, but as you hit more, your overall damage is probably higher. Some ships (and most players) have Chaff Launchers, which make your gimballs useless for a few seconds, which is why most people prefer fixed in PVP.
Also, many say that real men can aim properly and use fixed weapons. I personally prefer gimballed.
Just experiment with gimballed and fixed weapons and see what fits you more. You make no loss exchanging equipment in the outfitter, so feel free to experiment. I guess none of both are "better". Elite is about tinkering with equipment and ships and settle with what YOU like best.
Tip when swapping ships: Sell (or replace with E grade, as you cannot sell all slots) all equipment in the outfitter first, then trade in your ship. Trading in nets you with a 10% loss, so when you sold all the expensive equipment without loss first, you can swap ships and experiment with them with minimal financial loss.
EDIT: I should add, there are other viable routes to richdom. You can instead go the router Adder and Hauler for your Cobra, and earn cash with trading (easy cash) and mining (debatable, will be better with patch 1.3). However, that's a matter of taste, I personally can trade occasionally, but not exclusively else I die of boredom. You need to understand there are basically three categories of ships: 1) Combat (Eagle, Viper...), 2) Multirole (Sidewinder, Adder, Cobra, ...) 3) Traders (Hauler, Type-6, ...). If you have a ship of role (1) or (3), you are pretty much limited to that playstyle. If you have a multirole ship, it won't be as great as real fighter or a real trader, but can do pretty much everything in the game. The Cobra is a combat beast, though. Again it's a matter of taste what you prefer. Again, I personally like those multi-role ships, but you could also have a dedicated fighter and trader ship in your hangar and switch accordingly. So much freedom...
