Another option is to Exchange players ; you need 50,000 in value to get 10 points in Team Affinity. What I like to do is to buy ~13 cards with 78 overall = >50,000 in value. Most of the time you will find 78 overall cards for which you can make buy orders for 300. So for an investment of roughly 4000 stubs, you advance in Team Affinity. At some point you even get 200 Stubs back as a reward.
I know 4000 stubs is, for some of us, a lot of stubs but I found this to be the quickest way.