There is no definite answer that states how often you are supposed to hang out with friends. You may be looking for a definite answer because that's what you were taught in school. Something's either right or it's wrong. It doesn't work like that in the real world in many cases; the world is mostly shades of grey rather than black and white. There are some norms that are observable, however. You contact them as you feel the need to. But it isn't all about you, either. If they are going through a rough time, provide emotional support. There are many different levels of friends, too.
For the longest time I only had acquaintances. Then I started making more of an effort to strengthen some of these bonds. I invited them to certain outings every once in a while. This one friend I have seems to be on the needy side, for instance, so I will contact him every few days. This other friend I have is more laid back, so I contact him once a week, if that. This other friend who lives farther away we talk on the phone about once a month, lol. Even so, most of these meetings or outings are small talk or event-oriented. For the first time ever I currently have a friend that I contact every day. At least through text. If not, then we will ride over and see each other. And guess what? We don't always know what we're going to do. Just hanging out sometimes. Deeper than small talk, and not entirely event-oriented as sometimes we don't figure out what we'll do until the last minute. This is a different kind of friendship than I am used to. It seems to be presence-based. We actually enjoy each other's presence more than the event we're doing. We can be silent in each other's presence and be comfortable. This seems to be the world's definition of a deeper friendship which I am finally experiencing for the first time at age 23. Don't give up!