How often can I comment on her facebook status before being a weirdo? also...?

So I never really knew this girl too well but we use to talk occasionally like a year ago. we're fb friends and I want to improve our friendship without being too overbearing. how can i do this? I commented on her status and she commented back so that was cool. what else can I do? Also, is it weird adding someone you havent seen for like 3 years that you didnt talk to too much anyway? just curious. The first question is more important.