As someone already said, Exalt Barrel Maids would be an excellent purchase, along with a basic oring and spares kit for your markers. A basic marker stand can stop expensive accidents and I'd also be looking to have a second mask, which makes life a little easier if you get a bad mask hit and haven;t time to strip and clean between games/points.
I also find an old toothbrush is one of the best additions to my kit - makes cleaning paint out of awkward spots easier!