I haven’t touched MUT since week 2-3 after launch, so I’m currently at an 82 overall team with less then 200k coins. AKA, Harvest, and Legend challenges look like the best bets, but are there any better challenges I should do before those?
AKA Challenges will give you some players along the way and any non-LTD AKA player if you max out all the challenges. Don’t use any of the tokens on any set but the champion one or you will be short tokens. Legends challenges are similar in that you will get some mid players while completing the challenges. Once again, save all the tokens for a champion. You can eventually do this set twice, so you won’t need to complete all the challenges yet. The next set of challenges would probably be Zero Chill. Another good set for new players would be Hispanic Heritage challenges.
Honestly just whatever is current. If you have a good team then a lot of the challenges won't even give you a player that's relevant in the present let alone the future. Don't waste your time on anything before ZC except for legends and AKA just to get a couple bound champs.