Best thing I find doing if you're a team without much in the way of funds is look for people coming out of contracts. Thiago and Davide santon are both young good players you can pick up on free transfers with a little luck. Give them a few seasons and you could easily get 10-15mil for them.
You'll either have to stick with signing one/two big players with what budget you have available or go for signing a bunch of decent youngsters for fairly cheap. Advantage being you can get some very good young players that will pretty much triple in value over 2-4 seasons.