Moved from the TCG Competitive Play to the TCG Help & Advice, since the OP is looking for help regarding finding a new deck. ~bbninjas
Finding the best deck for you requires a bit more specifics. What type of deck are you looking for? One that can dish out a lot of damage? One that tries to slow your opponent down through locks? One that is bulky and has a strategy harder to defeat? One that has a strategy that is consistent and can be easily set up and played?
Is there any card or combinations that you are interested in now? Is there any requirements (i.e. fire types, budget)? Are you a competitive player (tournaments), or a casual player (just for fun)? What specifically does your fire/dark deck contain (since your description is fairly generic)?
Answering these sort of questions will make it easier for us to help you out! ^_^