Ditto all who have said buy what you can afford and what goes with the project. Even in LQS and with some name brands you will find fabric that isn't worth the price and at WalMart, JoAnn's, Hobby Lobby, etc., you will find great pieces at reasonable prices.
Keep in mind the number of posts you see on this board from people who are tickled out of their minds because they found a ton of fabric at a thrift shop or a yard sale. They have no idea where that fabric originiated unless the designer/maker is printed on the selvage.
Go for it, woman! You've got more guts than most of us to try such a demanding project. froggyintexas