If you have just started an IRA (presumably with a contribution for 2012),
you likely have $5000 in it, or $10,000 if you made a full contribution for
2013 as well. At this time, I would recommend putting it all in a
single low-cost mutual fund. Typically, mutual funds that track an
index such as the S&P 500 Index have lower costs (annual expense fees)
than actively managed funds, and most investment companies offer such
mutual funds, with Fidelity, Vanguard, Schwab, to name a few, having
very low expenses even among index funds.
Later, when you have more money in the account, you can consider
diversifying into more funds, buying stocks and bonds, investing in
ETFs, etc.
Incidentally, if you are just starting out and your Roth IRA is
essentially your first investment experience, be aware that
you do not need a brokerage account for your
Roth IRA until you have more money in the account to invest and
specifically want to buy individual stocks and bonds instead of
just mutual funds. If
you opened a brokerage account for your Roth IRA, close it and
transfer the Roth IRA to your choice of mutual fund company; else
you will be paying annual fees to the brokerage for maintaining your
account, inactivity fees since you won't be doing any trading, etc.
The easiest way to do this is to go to the mutual fund company
web site and tell them that you want to transfer your IRA to
them (not roll over your IRA to them)
and they will take care of all the paper work and collecting your
money from the brokerage (ditto if your Roth IRA is with a bank
or another mutual fund company). Then close your brokerage account.