Talk:Open Sky Challenge/@comment-197.15.254.84-20161005015547

I managed to unlock the next career series by buying the Atom 3.5 first, did some R$ upgrades and then I buying the Caterham (-20% discount) which has to be upgraded with R$ till max, reaching 60.6 PR. But it is a must to reach 61 PR to unlock the next series so at least 8 Golds have to be spent (brakes upgrade). Otherwise, you're stuck. Hope this helps...

Summary: The minimum Gold required to unlock next series is 8. R$ only streategy is simply impossible.