Dave, Bushwalker was bit blunt, but on the mark.
These things take time and come from within. People will give respect to those who have earned it, and close friends will shake out over time, but only if you are friendly and get to know people and are capable of being a good friend yourself.
Regarding the biker example - things like that tend to happen on their own. When I was a skater and dressed like one, it was only because I'd walk into the skate shop, see the clothes, and think "that's cool, I want that", and in short order I looked like a 'skater'. I never set out to do it intentionally, and I think that's the case for everyone who looks like something they are into (bikers, metalheads, goths, etc). Actually trying to look a certain way is being a poseur, and you don't want that.
If black looks good on you, it's something to keep in mind. BUT, the question is, do YOU like it?
It sounds like you have a lot more to sort out than just clothes, like Bush was suggesting. I was in a similar place to you once. I dressed how I did because I felt that everything else looked worse on me, even though what I DID wear, didn't look good, it wasn't as bad as other things. With that perspective, you will never get anywhere.
You first need to figure out what makes you happy. That's no small task. Start with your interests, and jut let go, enjoy them to the fullest. You should already know what your principles are, embrace them and don't be afraid of them. Talk to people, meet people, try to have fun at everything you do. Along with that, treat people how you want to be treated, and how they deserve to be treated. Don't give free passes to assholes, but also don't snap at people who don't deserve it either.
Don't give other people power over you. Don't let people ruin your good mood, or make you feel bad about yourself or ashamed. Nobody can make you feel bad or shameful unless YOU let them, unless YOU give them the power.
And when it comes to friends, be upstanding, trustworthy and responsible (this applies to all of life, really). Those who are worth your time will make themselves known. Those who aren't need to be kept out or cut loose. (don't be callous about it, just know that not everyone is worth your time) Even if it means being alone for a long time, it's just the way it has to be. If you hang out with people just to have company and hold on to them when you shoudln't, you will be holding yourself back, and never allowing yourself to grow and be happy.
Once I really understood a lot of that, I started gaining confidence. And at that point, I was able to actually look at things and think "hey, I like that, I want that". You have to clear the fog before you can see.
I now do things I never would have DREAMED about a few years ago - I chaotically spike my hair, wear colors other than black, wear sandals - and shorts - and any chance I get too, wear a toe ring and an ankle bracelet (and look damn good doing it), I got into some layering (which I never saw the point of before), and even wear
gstrings and see-through clothing for my girlfriend (on occasion).
But all of that came AFTER I cleared out the fog and made some internal changes first.