Why it is good to be risky
The reason why it is good to be risky is because risky investments can result in higher returns on your money. The problem with being risky, is there is a chance you can lose money. However, in the long term you can usually benefit from higher returns even if you have a few slip ups. Let me show you an example:
These two lines are based off of placing $2,000 in a retirement fund at age of 20 and then at age of 25 start investing $6,500 a year (based off of a salary of $65,000 with a company that will 1 to 1 match up to 5% IRA contribution, presumably someone with a Master's should be able to get this) and then being able to increase your contribution amount by $150 a year as your salary begins to increase as well.
The blue line assumes that all of this money that you are putting in a retirement account has a fixed 3% interest (compounded yearly for simplicity sake) every year until you retire.
The red line is earning a 12% interest rate while you are 20 years old and then decreasing by 0.5% per year until you retire. Since this is using more risky investments when you are younger, I have even gone ahead and included losing 20% of your money when you are 24, another 20% when you are 29, and then again another 20% when you are 34.
As you can see, even with losing 20% of your money 3 different times, you still end up with more money then you would have had if you stuck with a more conservative investment plan. If I change this to 50% each 3 times, you will still come out about equal to a more conservative investment. Now, I do have these 3 loses placed at a younger age when there is less to lose, but this is to be expected since you are being more risky when you are young. When you are closer to retirement you have less of a chance of losing money since you will be investing more conservatively.
Why it is OK to be risky when you are young but not old
Lets say you loose 20% of your $2,000 when you are young, you have 30-40 years to make that back. That's roughly $1 a month extra that you are having to come up with. So, if you have a risky investment go bad when you are young, you have plenty of time to account for it before you retire.
Now lets say you have $1,000,000 when you are 5 years from retiring and loose 20% of it, you have to come up with an extra $3,333 a month if you want to retire on time. So, if you have a risky investment go bad when you are close to retiring, you will most likely have to work for many more years just to be able to recover from your loses.
What to invest in
This is a little bit more difficult question to answer. If there was one "right" way to invest your money, every one would be doing that one "right" way and would result in it not turning out to be that good of investment. What you need to do is come up with a plan for yourself. My biggest advice that I can give is to be careful with fees. Some places will charge a fixed dollar amount per trade, while others might charge a fixed dollar amount per month, while even others might charge a percentage of your investment. With only having $2,000 to invest, a large fee might make it difficult to make money.