I don't know how much roleplaying experience you have but, here's what I suggest.
1stly, not to be mean but, you might want to start with getting approved first.
Then I'd focus on making a character, his personality, his favored weapons, and his background, instead of just posting on the fly. It doesn't usually work for threads such as this.
Playing an ODST is fine btw, and if/when you are approved, to make things easy, have your character go through the drop, explain your characters actions over the last two days, try to be a little realistic please, and then meet up with Spartan Adelaine and Private Matthew Fry.
I hope that I haven't offended you in any way and that your approval is speedy :)