TTG_Rizzle wrote Im in the same situation. The dreaded 10-20k mark.

My method:

1. Use ultimatedb.nl to check player prices

2. Choose a league to trade in.

3. Choose a formation. I usually choose 442, 433 and 41412 (basically trade in the good formations)

4.Once you've learned the average selling price, Buy low, sell high - It might take a little bit longer to find those deals, but well worth it

5. You can also use youtube for tips and stuff

Hope I helped a little if anything.