We don’t have cash registers or air conditioners which should we purchase first as we only have limited funds?

Cash registers would mean you can record what stock is sold, add security elements to your cash handling, speed up line service, and eliminate adding up off the top of your head. The scan type system is fabulous, so are touch screens but they cost a lot more.
Without registers you cannot track your stock. See fact sheet on website on cash registers for more information.
Consider a grant application for the air conditioners. To find out where and when the next grant writing workshop is go to www.kymkirk.com