In my 20s I felt very conscious about the number of friends I had, as after university I didn't really know how to go about making them.
I've found since meeting DH and having kids that it's all come a bit easily without consciously trying. I'm in my mid-thirties now and I have the following:
3 best friends from high school - chat every other day via WhatsApp, but spread across the world so only get to meet maybe 3 times a year
2 best friends from uni - chat once or twice a week via WhatsApp - live very far apart so only meet maybe 1-2 times a year
1 good friend from work - chat via WhatsApp every week or two, and meet maybe once a month, she doesn't live too far but not near either
3 good friends that are wives of DH's best friends - chat every couple of weeks, and meet maybe every 2-3 months
4 really good mum friends - WhatsApp most days and see each every other day
So 13 good friends, but have other more acquaintance type mainly mum type friends, and a few ex-colleagues who get the same train into work as me.
They say that you lose your mum friends quickly when you're kids end up doing different things/going to different schools etc. I'm not at that stage yet so we'll see.
I think as I've got older, I've become more confident and chatty and not bothered by rejection etc. when chatting to others.