being mediocre for a while. although i actually have nothing against people taking lessons from a good teacher. it's very important to learn how to breathe correctly, although it's something that you can learn yourself. there's a website with some good exercises and tips here.
but the bottom line is you've gotta practice. it's a case of working on weaknesses and strengthening your voice, but it's also to do with confidence. the better you get at it, though, the more confidence you'll have in your abilities.
anyway yeah, good luck in deciding what you want to do.