Only basic thing that comes to mind is: Don't buy $200 worth of stock. If you pay a broker $10 commission, you're already down 10% as soon as you decide to do it ($10 to buy and $10 to sell). Hell, even if you're buying $2000 worth of stock, you've lost 1% right off the bat.
The stock market is a casino for rich people, not us.
Anyone making an engineering level salary in the US should be saving a portion of their money and investing in the stock market. There are a wide variety of options that involve no commissions and allow you to own a broad cross section of the market. The Vanguard Total Stock Market ETF is a good place to start. As are Vanguard's age based funds and automatically reallocate to more conservative positions as you get older.
Writing off the stock market as a "casino for rich people" is a good way to make yourself poorer.
I wish there was a crash course on this when I was in college. I've been meaning to understand stock market, how to get involved. The most I got was 401k but I don't even look at my Fidelity. I know certain industries are projecting or doing well currently... but ugh.
The stock market is a casino for rich people, not us.