I hadn't heard of an airplane called " Nutball " before so I looked it up. Seems to be a few different versions including one with polyhedral. Looks like it would be an inexpensive project and the OP would definitely learn from it. Normal foamboard can be found at many Dollar or craft stores. I know that both my local Michaels and Hobby Lobby both stock it.
As for radio gear, motors, batteries and an ESC I would suggest you take a look at Aloft Hobbies. They carry everything you would need to outfit your project. My suggestion would be to buy a GWS Slow Stick from them with all the radio gear and accessories needed to fly. Start learning with the Slow Stick as you build your Nutball in a size that would allow you to pull the electronics out of the Stick and use in the Nutball.
https://alofthobbies.com/
https://alofthobbies.com/slow-stick-...tem-parts.html