Time for an intervention

Situation: I've promised myself no more yarn buying until the Maryland Sheep & Wool Festival, unless it's for handpainting for the business (but the business has no money after registering my name, so that's a pause).
Problem: I'm supposed to by designing a cardigan for Spun, but they haven't gotten back to me about a yarn sponsorship. I want to start the knitting, but I don't know what yarn (if any) they'll be sending me or what yarn I'll get if I buy it myself.
Resolution? I'll buy yarn to handpaint and use it for the design. I now have 3 different yarns in my shopping basket, each with enough yarn for a cardigan.
Do I get all three and use the one that suits the design best? (I could sell the ones I don't use in the design.)
Do I buy one and hope it works? (I could buy the others if it doesn't.)
Do I wait to hear back from Spun and risk missing the deadline for the publish date. (I could submit it somplace else)
Someone help!