I loved the Viper for combat. Whatever you choose make sure you can afford lots of re-buys. That is the good thing about those ships, you learn by making mistakes but making mistakes doesn't cost too much.
If your end goal is PvP then you should use fixed lasers on whatever you go for. It is hard at first but it is the only way to get really good. If you start using gimballed lasers then it will make it harder to change later.
The Viper with small fixed lasers and medium gimballed multi canons is a classic choice.