When starting out (really Season 2 on) the best way to get $$ is to buy and sell Free Agents, they will cost next to nothing $ wise, and if you look for higher value/younger ones they can either play in your team or be sold for $.

Try to shop for players in the "off" times of your server. Often it's late at night. But if there are less Managers on it's easier to get player without a bidding war.

Each team is given a couple really good players, don't sell them, TRAIN them as often as you can, give them an green booster and an extra training. (When you train your whole team you can see who gains the most from it concentrate on those players)