Imo when you are looking at buying 1 you have to choose a role that will be key to your formation. I'd guess price would be around 5million or more cos I'm level 3 and spent nearly 4kk on 1 the other day - 18yo, single role, no SA, 34Q. Ofc if you're going to boost him quickly then probably Hard Training is advised (not any more efficient than Normal just relatively quicker) and keep some red packs handy.

I'm sure others can contribute a more systematic approach or search for power training.