to answer your question, i'm also an filmmaker on a fairly low budget, and i've researched the topic of blood squibs. First of all, you must be licensed with the state to handle them. Second, these professionals for hire do not come cheap at all, most cost more than I and probably you can afford. I would look to use compressed gas bullet hits instead for your film. They can work just as well. Hope this helped

Condoms, runny ketchup (or your own mix), string, and some kind of very small explosive can work wonders