there are 2 ships to get started with combat imho:
1. eagle. the eagle will teach you a lot, but you will also loose it a lot in the beginning. the eagle is not especially fast, and it doesn't have good shields or hull for tanking - but it will teach you skill - to outmanouver enemies, to think ahead
2. viper mkIII. both shield and hull tanky for its size. probably the best "starter" combat ship.
take one of those to a nav beacon, pick your targets, and learn by experience.
if you have severe problems in the beginning (like i had), fit a small beam turrett with other weapons - it will show you where to turn to, and get the right distance.
after that, you might want to invest in a DBS, a courier or later a vulture.