StevenS1124: Should I upgrade my driver or irons first?
3WD before driver before irons, IMHO, but
First: Decide whether you want to play for free or if you want to chase or buy credits!
IMHO, any equipment purchase (clubs/balls) will probably accelerate tier advancement, so be careful what you wish for!
Second: Wedges!
This is because the Starter wedges are the worst of these free clubs, and any short wedges above L25 will make a big difference!