X45 budget surfing

I recently bought an 06 MC x45. We mainly wakeboard but are anxious to surf. We don't wish to spend a lot of extra cash this year on surf gear. Other then my stock ballast system, what bags would you reccomend buying first to get a decent wake. I'm told a 750 in the rear side locker. I would like to buy one more and was wondering which one and how big.

Thanks