if you want to go for pure combat. the eagle is quite affordable and easy to upgrade and much better then people thing, the viper is viable after about 1 million credits and the buy cost, but is more of a intersepter over a fighter so you need to pratice using its very high acceleration to make up for your slightly weaker then normal turn rate, especaly if you swap off the eagle, but its sheild is the best avaible on any fighter sized craft in the game, however its armor is squishy (slightly better then a eagle)
if you want the ablity to do both combat and mining or trading on the side, the adder and the cobra both are very good for whatever you want to do.
the adder is much better then people give it credit, as it has 1 medium and two small, and the offset between the guns is workable though, the cobra has about the same amout of weapons as the viper, however the outer guns are very far apart and outside of gimbles and vs larger ships, can be a pain.
if you want a ship larger then those, the asp is likly the best all around choice, it has plently of everything, the python is likly the best combat ship and also has lots of everything as well, just dont expect to be able to afford them any time soon.
lastly, if you want to bounty hunt, do so in style, get a orca.
