In dynasty mode, rack up on draft picks by signing unwanted free agents and trading them to random teams for draft picks. Doing this also earns you GM experience points.
Use the following trick to get high draft picks without trading good players. Once a draft is completed, see which teams took the first few picks and remember their names. Go to the "Trade Players" screen in the GM menu. The team that just took their first round pick will usually trade away that player for a third or first round pick. Note: You do not receive your draft picks to trade until the beginning of the next season.
You can easily make all the other teams in the league in dynasty mode go broke by simply trading them salaries. Go to the Free Agency screen and sign anyone desired (the worse the better) for long-term contracts and millions of dollars. Then, trade those players to the other teams. The CPU will accept any trade if they do not have to give up anything in return (for example, a trade for a 50 overall defenseman with a 6 year deal worth $25 million a season). Doing this allows you to sign free agents in the off season very easily, as no one else will be able to afford them.