In theory, I could have upgraded that many times before getting them. What I did was use the save method to test to see which set would give me the best. Turned out, set 2, upgrade 3 was the best, so it cost me around 550 or so.
3 sets, 20, 22 and 23. My question is how many rounds do you get before they "break" and is there a limit to how many times you can repair? I mean 10 gems is like 10 -15 mins work so I can handle that once a week.
I'm in the same boat. I've got all five sets. No matter what do it never gets above 22. I've figured out you can earn gems much faster if you have all the items unlocked. Buy from the shop copy them from on line profiles. Play challenge in serious mode will give you 4-5 hems each round. Lucky chance rewards default to coins or gems if you have acquired everything. I can usually earn 12 gems if I time the lucky chance right. 3 rounds of golf on tornado cup in under 20 min if I'm lucky. Yesterday I earned 40 gems in 3 hours.