It all depends on what your goals are. Promotion with a crappy team is also a fun and proud achievement. I just work with what I got and try to get the best out of things. Sometimes I spend so much tokens on bidding wars, sometimes I can get a very nice 18 yo 5* for 1 token, its luck.

I love the U21, the problem is that they are at best 4*. If you have a Scout team then he'll never catch up and you will waste more tokens on PT him. If your team is 5* or less, sign the bastard because I garantee he'll perform and train very fast.