Well I can tell you what you’re missing from what I’ve read: confidence. If you don’t like your voice, then you won’t get very far. Learn to love your voice and, in turn, you’ll learn things about it as you go!
As for the whole pigeon-holed voice thing goes, I can tell you that depending on what type of voice you have, it WILL limit your roles. For instance; someone with a fairly higher voice range probably wouldn’t be cast for someone like Master Chief or Duke Nukem. A voice ought to be justified, you know? The way I see it is; every voice fits for something. Find what works best for you and then expand on it. Focus on what you can do now, that’ll look more impressive if you’ve fleshed out your natural ability before you start expanding into different vocal ranges.
Now, that’s not to say expanding your range is a bad thing. In fact, a great deal of VAs I know personally have fantastic ranges and could tackle a good number of characters! That is something you can work on over time, but if you focus on fixing a problem that doesn’t exist, then you’ll neglect your natural talent and you’d be doing yourself a disservice by ignoring your god given ability!