I do the 3 division conquests first to get a bunch of packs with players to use for missions.
Then make sure your doing the team affinity 2 mini season for the vouchers. Priority goes to players with missions. Once you get all your guys with missions in the lineup, fill in the roster with future stars to go after the goals for free packs.
When you're getting further in team affinity and completed most missions then start loading up on one team. Look first to see what teams are close to completion. Pitchers gain pxp the quickest.