I think it'd be a good idea to kinda post a list in order of importance for courses you should try to purchase for 18k coins.

If you DON'T have the Collector's Edition
1. PGA National Champion Course
2. The Old White TPC
3. Pinehurst No. 2
4. Oakmont
5. Whistling Straits

If you DO have the Collector's Edition
1. Spyglass Hill
2. Predator
3. Banff Springs
4. Blackwolf Run
5. Atlanta Athletic Club
6. Liberty National
7. TPC San Antonio
8. Waialae

In 45 days, you can also work to unlock these courses (Gamestop / Best Buy pre-orders) -- would like to play these courses maybe in season 3
1. Wolf Creek
2. TPC Blue Monster @ Doral
3. Emerald Dragon