Probably get hell for this, but, I'm in the same boat (finance wise). I've been using Apple Barrel craft acrylic paints from Walmart to practice. I found reducing the paint with generic glass cleaner (no ammonia) works great. Less tip dry then plain water. As far practice material, If you have a "Dollar Tree" in your area you can get a big cardboard display board for a dollar. I cut them up for practice and protect the walls from overspray. They might be a bit thick for stencils?