Hi Jolene and welcome!
For $500 it is going to be tuff to get both! Unless you make them your self. I would go to a local manufacturing business and see if they have tubing drop off they could donate to the school for an English wheel frame. 3x6... 4x8 I would try to get as thick as possible if you go with a smaller tube. If you do search you will find many builds with dimensions.
Good luck!