I usually aim for the middle arrow or one to the left of it or in between.
Good. You're looking at a target on the lane instead of only at the pins. It is the target on the lane, when your ball comes off right, that gets your ball into a roll. Yes, there is a lot more going on than just that, but as long as you're looking at a target instead of just going straight for the pins, you're on your way.
I am 17 years old. Also, I am going to a bowling camp this weekend and on the paper to sign up, it said that they would help to make sure our bowling balls are the righ fit.
Glad to see that you're going to this camp. While we all know that you are already at this level, I'll just say it again just for affirmation: Be open to the suggestions the coaches give you. If they are doing their job (and to be honest, if they are USBC Certified, you should be able to check their credentials at bowl.com), they should be able to dissect your game to its minute levels, and help you to build it up to where you can be competitive. But it will all start with you and going into the camp with an open mind. But also with that, you'll need to tell them what you want your end result to be. If you want to be as competitive as your Varsity team, tell them that, so they'll know how much they should help you and what you need to work on.
At 17, they may say that a 9-pound ball is definitely too light, and give you recommendations on what you should have. They may even have something for you to try while you're there. If not and they do recommend a heavier ball, ask them which ones you should go for, type of grip (conventional, fingertip, etc.) and take that info to your local pro shop. With that info, you'll know what to get and get it fit for you.
There's plenty to go off of here, and I know the info may be overwhelming, but it will definitely pay off in the end, especially if you are wanting to do this (which you are).
Keep us up to date on how you're doing!
BL.