Ugly Stick. Bout as basic a 2nd airplane can get yet provide a lifetime of fun flying. I'll always have one in the inventory. I also have a flying wing and a trainer. Look, don't get rid of the trainer. They really are fun to abuse. Build a rato pod for it. Put a bomb drop on it. If you have a single flap servo widen the bay a bit and put two servos in it so you can play with flaperons. This if we're talking balsa. If you're talking flite test try a Scout a Versa or a Bloody wonder. When I get back from my indoor fly next week I'm going to order one of the Hellcat kits and put that together for my front yard (I'm in the country, it's about an acre with an unfortunate Hedge tree on one side I'd get rid of but, it's gotta be a good 50-75 years old-but- it does have thorns on part of it)
What specifically are you talking about for you trainer and what size/power are you looking to move into. Even the plane in my photo is a Stick, albeit gas powered and made out of Coroplast (plastic campaign sign cardboard). Funny enough, the SPAD UltraSpadstick pictured builds remarkably similar to a flite test plane.
Tell us more what way you're going. What type of building you're looking at. IF you have a club your using and if that club has an FAA approved flying site. I'll talk smack about that all day long in the end though I want as many pilots out here as I can get cuzz we're a dying breed.