I believe I have found some ways to get all 10 set pieces.
This is building on the assumption that you after you go to chest phase and open 6 chests, that you are allowed to continue open 6 chests again and again (as long as you have pots of gold) AND that every time you will recieve a kit from the 6chest bonus.
So in order to get all 10 pieces, you would have to
- Do 100 tasks; This gives you the grand prize 4 times of which 2 are kits.
- To do 100 tasks you need to finish town minimum 3 times. (Avarage 34 tasks per round, 34x3 = 102 tasks, so you dont have to do them all )
- You have to open 6 chest 5 times. You can either do that 5 times in a row, or you split it between the repeats (e.g first time do it once, 2nd time twice, 3rd time twice again).
Now you have 7 kits from grand prize, chests and 3 from quests.
This will cost 2930 pots of gold (for town repeats) + 9500 (for opening chests) = 12440 pots of gold
OR
You can just do ONE round of the town which will cost 980 only (granting you one kit) and then do 6 chests rounds in row (assuming that is possible) which costs 11400 = 12 380
Either way, it will be more pots of gold than we get for free.. Im sure you can do some other combinations, but I think you won't get much cheaper than that, considering our time frame.
But since I'm not interested in one of the upgrades, I could go just for 9 kits with the 2nd option and that would only cost 10 480.