3) While a lot of sports supplements are junk, I spend money on a good multivitamin, whey protein, and a quality fish oil. Anybody who tells you that stuff is junk is a moron.
Ok, well that stuff is not so bad...
It sounds like you've got a bright future but you really ought to listen to what everyone is saying here. The time to build up savings is early. Most people can't do that because they need all the money they can get to eat while in college. And many of them take out big loans with the hope of repaying it later from a big salary.
In your case you have money now but you have also chosen a career that, while it is admirable, does not pay extremely well. $50k seems like a lot when you are an 18-22 year old college student surrounded by peers that have very little. But it's not that much when you have a wife and kids to support, are stationed far from home and want to make the most of visits, etc. etc.
I think someone else made a very good point as well - what are you going to do when you fall in love and your partner has a career as well or just doesn't like moving around every two years or having her guy off in some scary place all the time? You can say what you want now but don't you think it would be good to prepare yourself financially for choices later? When you're done you'll owe the army 2 years or 4 years or 8 years or whatever. But after that time is up, don't you want to be in a position to choose what you do after that? Do you really want to have to stay in the army because you don't have the financial resources to make any other choice? I mean, even if you love the army, don't you think you will love it even more if you stay in because you want to rather than because you have to?
I had to work and didn't have a lot of play money in college yet I had a lot of fun anyway! I'm not suggesting you save all your $500 a month but I am suggesting you save at least half of it!
In any case, good luck.