Here are some tips that'll sure to help. Most of this stuff is beneficial for Matchups.
01. Make sure you go through all the missions. This is the quickest way to get a bunch of gold balls early.
02. Play "Matchup" a lot. You tend to get more gold balls by playing against another player online. I'm up to about 30,000 gold balls and a majority of it is by playing matchup.
03. Get all types of gear. I know they recently released package uniforms, but that's not necessary to be good at the game. Try to find out what style works for you, power, control or balanced. IMO, there are pro's and con's for each. i.e. too much power makes the homerun travel too long, hence wastes too much time, but not enough power might make you too short on crashes. Plus it's not worth it if the shot isn't a monster shot.
04. Crashing and consecutive HRs are more effective. The best way to accumulate points is to master crashing, i.e. hitting scoreboard, billboard and lights. I know cycling is also an effective way to get more points and fast, but the downside of cycling is that it takes too long in-between bats because the batter has to call his shot.
05. Play people with a higher rank than you. If you're at the stage where you want to work your way up the ranking list, try to play those with higher ranks. For one, you don't risk losing as much win points, compared to playing someone who's way lower. I'm currently in the 200's in rank, so I try to only play people under 5000. Winning 5pts isn't worth losing 15pts just because I lost to a player ranked in the 10,000's.