I was scared about making friends too, I totally forgot how you do it! But just put yourself out there a bit, sit in communal areas when you first arrive or something, people will probably say hey to you, and everyone's in the same position!
The sort of people who comment on the Facebook pages tend to be those who are pretty wild, and have the confidence to be posting about it! There are many people at uni who don't drink or have casual sex, and a great way to meet people with interests like yours is to join societies early on. (I know this is scary, but definitely worth it!).
Don't worry, and enjoy university life!