Here's the situation. I want to unload some items I'm going to have in a store. Let's say I have 3 categories - A, B and C. I want to sell the items in C as quickly as I can. I'd like to set it up as follows:

Order 1 from category A or B and get $2 off any item from C.
Order 2 from category A or B and get $4 off any item from C.
Order 3 from category A or B and get $6 off any item from C.

I've been looking at Better Together, but I'm not sure it'll do the trick. I'll probably only start out with 2 categories, but a third should be added soon.

Any suggestions?