RE: Going from RC car to RC gas plane... which one?
Pick A trainer .40-.60 sized please be advised that 300. will not be enough to get you completely started especially if you are building it from a kit. Believe it or not but RTF Packages are cheaper the building the plane from a kit. SPADS are a less expensive route check over in the SPAD Forum.
I'd be willing to bet that after Club membership and AMA membership your initial investment will be around 500.00