@samuel53 To answer your question in the most basic way, you aren't wrong if you're saving and asking these questions to begin with. Wrong is blowing your paycheck on restaurants, fancy cars, stuff like that. You're right, but financial right is a spectrum.
You're not going to find much support here for individual stocks. People around here prefer to do the index thing, though every once in a while you hear some alternate opinions. In theory, yes you can make more, but in practice it is very unlikely that the level of effort needed to do that effectively is worth it for you. Definitely read as much as you can about all of that stuff.
As a young enlisted, you have a wealth of options to you now, I suggest that you really consider carefully your "game plan." People have a lot of different ideas of what financial success looks like, and it might be different for you than for me. Do you want to retire early? How early? Or would you rather work till a "standard" retirement age and reap the extra savings. Do you plan on having kids, getting advanced degrees, getting married, donating large amounts of money to charity, living on a farm, etc.
Goals that you come up with are going to affect how you save to some extent. If you don't have answers to those questions, that's also fine! Imagine yourself in maybe 4 or 5 years, and think of what that guy might want. I've found that's easier than trying to figure out what 60 year old me wants. But getting an idea of what future you might want is the key to deciding how your investments are going to help that.
The only "technical" advice I'd give is to put a lot more into your TSP if you can afford it, preferably the Roth one*, starting now. There's a lot of info out there that shows TSP is pretty much one of the best investment vehicles on the market, (as long as you stay out of the G fund, which it sounds like you did, so good on you!)
Changing your investment percentage to 20% would only be about 150 per paycheck, which as a dorm dweller is really not bad, and still should leave you with quite a bit of extra cash to invest as you see fit, build that emergency fund, and do fun things, as long as you budget and don't try to keep up with E4 Snuffy and his fancy sneakers, mustang, nicotine addiction, and daily monster.
Good luck!
*Roth is almost definitely going to be better since your income as an E1 is very low, and roth benefits low income more.