Glad you enjoyed it !
I started years ago, in the same way. Went on a friends birthday, then a stag do etc. Got to like it, my first purchase was a Dye Invison mask, which had a thermal lense. I used it for regular days paintballing, and it made the whole day a lot more fun as people have said.
Anti mist spray will help, try online or halfrauds etc as its used for motorcycle helmets sometimes. I used it a fair bit, everytime i cleaned the lense. It does help, but its not a cure.
Ive never had a thermal lense fog up, no matter how damp and humid its been.
Off all the people i know who gone on paintball days, this is ALWAYS the complaint, the mask steamed up.
As said, paint is where sites make their money. As unfair as it may seem, they have to make a living. Ive never know any site to allow you to bring your own paint.
The exceptions are called walk ons. For players with their own stuff. And some sites still insist you buy site paint.
A walk on will be a fee, which normally includes lunch, and the days play. And balls are either supplied a lot cheaper, or you can bring your own.
Most sites ive played at, say they dont really make much from walk ons, but do it more to help the sport etc.
I hope you enjoyment of paintball continues, be prepeared to end up buying your own marker, becoming obssesed etc