If you don't want to spend money on something you can get for free, just keep using bronze players and discard of them when you've ran out of contracts. Keep buying bronze packs, and building a gold squad on the side with the extra money you make. You will
build up contract cards for your gold team.
Try and win tournaments for bonus coins.
This is the fun of Ultimate Team for me personally, building a team from scratch. I've done it on the last 3 Ultimate Teams, paying for packs is a waste of money in my eyes.