So my understanding in this is that if you already have the credits on hand and use them to fund a tournament, that doesn't count towards the TIR goal. However, if you buy credits, does that count towards the TIR goal?
Nope, just the opposite. Buying credits gets no TIR.
Using credits does.
(of course, if you have no credits on hand, then you need to buy them first, then use them)