"When should I start buying PSAs?"
You can start buying PSAs straight away you can also win them in bid and build when you enter the auctions.Be aware though that in either case you can not guarantee that they will be active and if you choose the buy option you could be spending money with no gain.
I prefer to use the second option bid and build that way I am earning vp and If I get a PSA that becomes active its a bonus! Also try to recruit from amongst your family and friends
