SClittlefield has cheap, but good, 1.1 ripstop for 3-something a yard. I've made all kinds of stuff out of it. Noah Lamports (?) has Sil-nylon for $3/yd if you buy 10 yards or more. (Sil is wicked-slippery stuff)

You don't need a ton of fabric scraps to play with... just enough to understand the quirks of your thread injector with various fabric weights.

Personally, I'd make 2 stuff sacks, then move on to a hammock (lots of practice with a rolled hem,) Tree huggers, and then move on to a tarp then a G4 pack or a quilt project. By the time you're done with all that, you wouldn't be an expert, but you'd be skilled enough to tackle anything you'd need for hammocking/backpacking.

Welcome to the addiction!