If you get to the club, I'm betting that $300 will get you a really good used trainer, with engine and radio equipment, and maybe a few other field items too.

Slope soaring is basically flying a glider at the edge of a hill (at the top). You use the wind coming up the side of the hil for lift. Many are not gliders in the typical sense, but can be warbirds or whatever. Just without engines.
Dennis-