I'm not calling these truths, just musings. As such they could be totally wrong, so don't hesitate to disagree!
When you have only had shitty friends, you don't get a chance to learn all the friendship skills, because a friendship can't go beyond the most skilled one in it (unless you mutually work on it). So if you are a level 2 with only level 1 friends, you can't move to level 3. If you're a level 1 with level 1 friends, you could both move to level 2 if you both decided to build that skill. Some of friendship is about intention, but a lot of it is about experience.
I think that people are composed of their experiences (and don't have much power over what those experiences are) so all you can really do is seek people who are similar to you in level, want to grow in friendship, and aren't so privileged or prejudiced that they can't see you as a person - and hope you get lucky. This is obviously easier if you are in a category that isn't routinely dehumanized and othered. Many more people are willing to invest in you when your looks and identity are something they feel comfortable with. Just from my relatively privileged experience, it was SO much easier to find friends when I was thinner and identified as a monogamous straight cis person. Also I am beyond lucky/privileged in the fact that I got to go to therapy for two and a half years, and got plenty of time to write and learn how to hone my communication, and more than anything else I was able to find people who were on my level but ready to move to the next and willing to do so with me. You can't create friendship skills without time, energy, and people to teach you and/or practice with. So, if you have few friendship skills it doesn't actually say that much about you as a person, necessarily. I think it only matters how you react to a chance to learn a new friendship skill.
I see four levels of friendship experience.
1) spending time together (not sharing deeply) in fun.
Most people exist at this level of friendship; at this stage a very close friend is one with whom you spend time with regularly or at length. At this stage, to feel close you have to be in-person and get things like smiles, laughter, hugs, overlapping energy, silliness, and play. You need (nearly) all interactions to feel good, because the only bad-feeling things that nourish a person involve sharing deeply. If something feels bad about spending time with a person, they no longer count as a friend, because they're not doing the things that you consider to be friendship (sharing fun time).
2) giving emotional support/listening.
This next step often still requires spending a lot of time together for closeness, because people in the first stages of vulnerability often need the immediate feedback of in-person or real-time communication. Saying something vulnerable and then waiting is often much harder than saying something vulnerable and having immediate response. For people in this stage, fun is still important, but it is also important to be able to express your negative feelings and have them held safely. People in the first stage can do this rarely if someone in massive crisis, but more often and they're gone; people in the 2nd stage consider supporting each other emotionally to be a vital part of friendship. I dunno if this is true for others, but when I was in this stage, I had a very hard time balancing my support for others with my own needs. It was like receiving support was so important to me that I imagined it as just as vital for everyone else, and I couldn't manage my own boundaries because it seemed so terrible to ever say no to a support need. This got me into trouble a lot.
3) giving feedback in a way that sparks new self-understanding; inspiring each other.
In this stage, spending time together for fun and support has decreased in importance. I think that a person has to receive a certain amount of support for a certain length of time in order to move to this stage. I think ideally, your parents would give you enough support in your childhood that you could go into adulthood in this stage of friendship, but I've never seen that happen. The people I have seen in this stage at early adulthood had unusually supportive friend relationships early. For me, I got to this stage through the unbelievably kind and generous and faithful love of my LJ friends throughout the time I was working through childhood sexual abuse. Support is no longer a strong need for me, because I once hit that critical level. I think it is possible for people who have not yet hit that level to still very much value feedback that leads to new self-understanding, but I consider the level marker to be when it becomes more important than emotional support. At that point, you seek different friends and different kinds of interactions. Instead of seeking comfort first, you seek friendships that push you out of your comfort zone. You have a new set of goals in friendship. Support and spending time is of course still a need and important, but it's not primary. It becomes more important to be able to learn from and about each other.
4) challenging each other and responding positively; mutual accountability.
This may not be the final level but it is the deepest and most intense one I have witnessed. This is when not only do you value each other's feedback, but you hold each other accountable to the values that you have decided are important (not necessarily the same ones). For instance, Kylei values a broad sense of community and I do not, so in this level of friendship I would pay attention to whether or not they were investing in broad community, and point out any way I could see that they could invest more. Likewise, I value creativity, and someone could check in on me to see if I was living up to my value and creating regularly, whether they valued that for themselves or not. This level requires a lot of time and energy as well as skills in self-awareness and observation of others.
A person can have friendships in different levels with different people of course. I have the skills to do #4, but don't engage in it often because it takes a lot of energy from both people, and it has been a very long time since myself and someone I loved had both the skills and energy for #4 at the same time. I still employ those skills sometimes but I'd say that most of my closest friendships are #3 with some rare #4 bits. In an ideal world I think all humans would have a #3 friendship with each other, and have at least three #4s in their life. But logically, that is impossible in our really fucked-up world; we need to dismantle hierarchical oppression first. I have no intention to get to level #3 with most people, and I can't imagine ever having the energy for more than three #4s at once. Those I have a level #1 or #2 connection with are still very important and I try to maintain those too - but I would wilt and feel lost without my #3s.