Pay off your student loans - use it for college tuition, books, living expenses. If you have debt, or are accumulating it, you don't need to be investing. However if you must invest, retirement - ROTH, not traditional IRA, in mutual funds. If you invest $100 each week, starting at age 18, until your retire, you will have over a million dollars at age 60.
ROTH IRA you pay taxes on the income before you deposit it, but the growth and the initial deposit has no taxes when you withdraw it. There is no capital gains, etc on IRAs. On traditional IRA, the money is pre-tax, and all of it is taxed when you withdraw it, as income. This is the best long-term investment, short of your education that you can make. Also, only $5000 max per year in any IRA until you are over 50.
If you have debts, you should not be investing. Single stocks are not a good idea, however mutual funds can be a great idea - you can buy a group, each month, depositing more into the account, and buying more blocks of the entire portfolio, not individual companies. This allows your to own a piece of a lot of companies, without having to buy individual, and often expensive shares. Look into the prospectus, that will show how the group has performed over the past 5, 10, 15 years. Investments should be long-tern, buy and hold for 10-30 years, not short sighted, buy now and sell tomorrow or next week.
Some people make money doing short term buy/sell trading, but it takes skill, training, knowing what to watch for, not just the price, but what is going on inside the company, what they are planning to do, to make a lot of money, or might be about to lose some. Buy low, sell high - that is the trick, and many people don't do well at those speculations. Also, you need to track the purchase and sale price as you make those transactions, and report the gains or losses on your taxes.
Your first investment should be to exit school owing the least amount of money. Next, you need to save, at least $1000 for emergencies, and eventually build that to at least 1 year's wages, before you start investing in anything else, besides retirement, then housing, future vehicles, family, and other major purchases, and then start building wealth - investing, when and while you have no debt.