I'll chime is and say joanns isn't all evil. You can pick up fabric there cheap to practice on.
If you do get fabric at some mass merchant fabric store like that make sure you get enough to finish everything you want. They buy fabric by the lowest bid so ACU this week might be produced by company X and next week might be company A. Both are "ACU" but will have subtle pattern differences you will not notice until you have the 2 side by side and it sticks out like a sore thumb. I've even ran into color shift problems with fabric from the same manufacture from 2 different dye runs.
I know some of the tricks to hide that stuff doing upholstery work but I didn't pay attention in the self taught class that day yet to learn them doing kilts.