Welcome from another Houstonian. And congrats on establishing good savings habits at a young age.
My two cents on your questions...
Keep the questions of where to put your stash and the allocation of funds separate.
But first, check out the FAQ and search features to identify recommended reading. The forum advice, while generally good, by its nature tends to give tips in bits and pieces. As someone starting out in investing, you will benefit greatly by more comprehensive study on all of the relevant considerations of household money management, savings vehicles, asset allocation, tax considerations, etc. The book that opened my eyes at your age was The Only Investment Guide You'll Ever Need, by Tobias. You can move onto more complex strategy books later.
With a better grounding in the fundamentals, take the time to write down a five- and ten-year strategy. Not just a target number, but an outline of how you think you can get there.
Tackle the "where" question next, researching the breadth of fund offerings, typical funds loads and expenses, etc. What seems like a tiny difference in expenses makes a large difference over time. TSP certainly excells in this regard.
The last piece is finding the right funds at your chosen "bank".