I can only echo what Eliod has said. The OP pretty much says it all.
Lighting is key
Find a setup that works well for you and keep using that (once you find what works, you can always experiment but at least you have a baseline to come back to.)
No shame in trying to copy the styles of selfies you like - that's how you learn.
If you don't yet do any processing of your pictures then now is the time to learn. Get Google Picasa (which is free) and experiment. The...