After the first round of drafting (which will be determined randomly), the person drafting the cheapest player in round 1 will get 1st pick in round 2. After all the picks from round 2 are in, the person with the lowest combined salary (from rounds 1-2) get first pick in round 3, etc. If you go crazy and draft an expensive Bonds and '80 Brett with your first two picks, you are probably going to be drafting last (or near last) for a bunch of rounds.
By keeping your total salary lower, you will be drafting early each round... including the expansion bucket draft in round 25.
Hope that's clear enough.