What comes after a Trainer?
Look for a plane with a semi-symmetrical wing, or at least a thick symmetrical wing. A shoulder wing would be best, but there are some low wings that will fit these parameters. Talk to other club members, see what they are flying. Some even might let you fly theirs, on a buddy box of course. Stick planes are ugly, but you'll be hard pressed to find a better second plane, I had one. I keep going back to them every so often, I have a gas powered one planned for next winter's building. Good luck.
Dave