Whom should I care?

I read this somewhere - "Don't let someone be your priority when you're just an option for that someone".

This affected me so much that I spent days pondering over it. But it was actually better than ruminating about people who don't spend any significant amount of time thinking about me. There've been so many sleepless nights wondering about some of my friends whom I consider close enough; about something that worries them, annoys them, exults them or whatever be it. But then I failed to realize for so long that I can only go half-way, and that I can't meet them unless they come half-way the other direction. I usually like to put friends into three buckets:
A. Friends who're really close and whose reaction to a random situation I'll be able to guess.
B. Friends who're not too close, nevertheless we like each other and our wavelengths match.
C. Friends who're just acquaintances and I'm usually not too bothered about what they do.

"A" are normally not a problem, "C" could be a problem, but I don't care. But those in the bucket "B" are people whom I like, for whom I care and about whom I'm bothered. The problem is those in my "B" might not be having me in their "B", I could be even in their "C" (whether I could be in their "A" is a difficult question to answer, it's totally subjective). I can knock at their doors and wait for sometime, but then, I should start walking back at some moment. As I walk, I can even turn back every now and then to look if the door's opening, but beyond that I have other things too, there are other people who're bothered about me and I need to respond to them. After some thought, I think I have classified friends into how I need:
1. Friends for whom I'm a priority.
2. Friends for whom I'm definitely an option, but not a priority.
3. Friends for whom I'm just an option or not even an option.

The A-B-C classification was based on what they're for me, but I guess I need to quickly learn about the 1-2-3 classification, which is based on what I'm for them. I think I know whom to place where, but I want to find out soon enough how exactly to befriend them, how much do I care for them, how much do I bother about them and how much do I actually think about them. I only hope that I don't misclassify people and that I don't lose some of them because of the misclassification.

I'm already starting to feel I've got a lot of time these days because I've almost stopped thinking about some of whom were a priority to me but for whom I was probably just an option. I can instead use this time to think about so many of those who don't have anyone to care about. I think I'm proceeding in the right direction, to what I should be doing when I'm 40, to what will give me the feeling of bliss, probably for which I came to exist in this world. I want to, as early as I can, stop doing things that I'll not be doing at 40 and start doing things that I desire to be doing at 40. What exactly is it? I'm still trying to find out.