I'd spend it (and then some) on fabric LOL but agree that if there are items you look at and say, oh no I couldn't spend that on me YOU SHOULD. Whatever that may be....a pattern you adore, some new shears, a stack of ribbons and trims, the latest must have notion, pincushions (I'm a pincushion addict so had to add that one), baskets for organizing your stash, etc.
I just purchased organizers for my stash when my in-laws sent birthday money. Best purchase I've made in quite a while and helped me to get moving on de-cluttering my sewing room.
Have fun!