Stay away from the "Dura" line of planes. They are not built through conventional means, and will give you NO building experience.

Since you said that you have not "Mastered" your trainer yet, I would suggest 4 planes (in order of skill needed to fly):

Easy:
Great Planes Easy Sport
Goldberg Tiger II

Slightly More Advanced:
Great Planes Rapture
Sig 4*

All four are just great fliers and they build very well with easy-to-read, step-by-step instruction