Firstly, what site are you playing at, walkons site (where players bring there own kit) or a commercial/rental site ?
Secondly, you need to make sure if the site you intend to play at uses air or co2.
Regardless whether you intend to play every weekend or every two months, owning a nice setup will make the playing experience worth it.
Unless you goto a walkon site, which allow any marker, there are some commercial sites do not allow electro markers, or even compressed air.
Listen to the guys above, get yourself a good mask, dont go cheap, try a few on for comfort, nothing worst than a cheap mask fogging up half way through a game, or you feel uncomfortable during the game.
Buy a cheap setup, you may as well use rental gear from sites.