If you are after your first bow kill, I wouldshoot the first deer that doesn't have spots and that presents a shot.
A BIG part of bowhunting begins AFTER the shot and the sooner you get started the better bowhunter you will become.
My first bow kill was a young and dumb spike. The only thing in the woods that day that was dumber was me.
But since then, I have progressed to where I only target the "alpha" doe. She is the one in the bunch that is usually trailing the others and a lot more wary and wood savvy. I do this because the challenge makes it more fun and I have plentiful deer and shot opportunities.
But again, if I was you, I wouldn't worry what size the deer is, buck or doe, until I got a few bow killsthat include successful and timely recoveries under my belt.
Good luck this season.