It’s a little bit of a crapshoot, but put it this way – historically more wealth has been created in the stock market than in any other modality. It is subject to crashes, as we know, but statistically speaking, over the long term, it rises in value faster than other vehicles.
I think with a 10 year horizon, and with $20 grand, you could be very conservative and buy long bonds, or you could do some risk-taking and invest in an indexed Mutual Fund, tied to the performance of the overall market.
I’m 60 and penurious, so I’m staying out of stocks, but you have more choices. If I were 20 years younger I would stick to the Fund. Don’t mess around with managed accounts or fee-per-trade accounts, because you’re not sophisticated enough to watch those fuckers (neither am I.)