A good question -- there are many good tactical points in other answers but I wanted to emphasize two strategic points to think about in your "5-year plan", both of which involve around diversification:
- evaluate your potential expense allocation
- evaluate your potential income
You have several potential expenses. Actually, expenses isn't the right word, it's more like "applications". Think of the money you have as a resource that you can "pour" (because money has liquidity!) into multiple "buckets" depending on time horizon and risk tolerance.
An ultra-short-term cushion for extreme emergencies -- e.g. things go really wrong -- this should be something you can access at a moment's notice from a bank account. For example, your car has been towed and they need cash.
A short-term cushion for emergencies -- something bad happens and you need the money in a few days or weeks. (A CD ladder is good for this -- it pays better interest and you can get the money out quick with a minimal penalty.)
A long-term savings cushion -- you might want to make a down payment on a house or a car, but you know it's some years off. For this, an investment account is good; there are quite a few index funds out there which have very low expenses and will get you a better return than CDs / savings account, with some risk tolerance.
Retirement savings -- $1 now can be worth a huge amount of money to you in 40 years if you invest it wisely. Here's where the IRA (or 401K if you get a job) comes in.
You need to put these in this order of priority. Put enough money in your short-term cushions to be 99% confident you have enough. Then with the remainder, put most of it in an investment account but some of it in a retirement account. The thing to realize is that you need to make the retirement account off-limits, so you don't want to put too much money there, but the earlier you can get started in a retirement account, the better. I'm 38, and I started both an investment and a retirement account at age 24. They're now to the point where I save more income, on average, from the returns in my investments, than I can save from my salary. But I wish I had started a few years earlier.
You need to come up with some idea of what your range of net income (after living expenses) is likely to be over the next five years, so that you can make decisions about your savings allocation. Are you in good health or bad? Are you single or do you have a family? Are you working towards law school or medical school, and need to borrow money? Are you planning on getting a job with a dependable salary, or do you plan on being self-employed, where there is more uncertainty in your income?
These are all factors that will help you decide how important short-term and long term savings are to your 5-year plan.
In short, there is no one place you should put your money. But be smart about it and you'll give yourself a good head start in your personal finances. Good luck!