I think it depends on how easy it is to make an arrangement with those that you seem to do the contacting. If they are happy to commit and stick to an arrangement, say a face to face meet up, that is at a time and location suitable for both of you then it's not really one sided. It may just be someone who doesn't initiate contact but is happy to get together when someone else initiates. But if it's difficult to make the arrangement, or you have to be the one to put yourself out, for example, taking time off work and travelling hours for a short meet up close to them or it never happens then it's possible it is one sided.
It's wise to give some space between making contact to give them time to get back to you, say if you left a message. Also put more time and effort into those that who either initiate contact as well or are easy to get together with and let those that aren't go to a lower level of friendship.
Good luck