The LT40 is a good choice to start with and once your flying skills improve next would be a Stick(Sweet Stik, Ugly Stik, etc..) . I would recommend the Evoloution 10cc gasoline engine . Ive been testing one and just waiting for a good day to maiden the plane. This engine is well thought-out and the supporting components are reduced in size to fit in smaller airframes, and the price is right too.

www.horizonhobby.com/products/10cc-60-cu-ingas-rc-engine-EVOE10GX