I find gas to be much simplier than glow, you won't have any problems there. Any 20cc-size gasser will work fine. Look at the Zenoah G-20 or the DLE-20

As for flying, you'l also find that to be easier than your trainer. You need the self-righting characteristics of a trainer at forst, but one you know how to fly, you'll enjoy flying a plane that goes where you point it and that you don't have to fight it's desire to fly straight and level