I also started with electrics and moved into nitro. Best advice I can give: no matter what nitro plane you start with, have an experienced pilot put you on a buddy box for the first flight! Even a slow .40 sized nitro trainer is propbably going to surprise you how fast and responsive it is. This is also the best way to learn what you need to learn about glow engines and proper tuning

You'll get a lot of different answeres on the best plane to start with. My personal reccomendation is the Hobbico Avistar with a .46 engine. It is a great trainer, but is a more capable aerobatic plane than most trainers due to the semi-symetrical wing and less dihedral. It's not as floaty and goes where you point it. This means you won't get bored with it as quick as you might with a Nexstar or some other plane because the Avistar is capable of a lot more as you get comfortable with it.