Ok - the credit card doesn't look too bad, IF you pay it off in full each and every month. If not they'll give you a "pants-on-fire" 22.99% interest rate, which includes all NEW purchases. So whatever you do never, ever be late and you'll be fine.
Also, you don't need to use your credit card extensively to get a good credit history. You could use your card once a month (and pay in full) and that would be sufficient. It's the history of
payment, not the history of
use that matters for your FICO score.
The stock market has/was on a tear from 2010-2013. It had greater returns than almost any other 4 year period in the last century. Yet recent polls have shown that about a third of american think the market went down during this period, and more than half said down or flat. There is a shocking disconnect between perception and reality in this arena. I don't want to get this off-topic but most Americans have lots of debt, no savings, and no clue what the markets are doing and how compounding interest can save (or kill) their financial freedom.
Regardless, since you have a decades-long timeline, I'd strongly encourage you to park your IRA money in a low-cost index fund. Vanguard 500 is a popular choice here (and the one I use)
https://personal.vanguard.com/us/openaccount?CompLocation=WWOIRA_Tab1&Component=OpenIRA_Body&acctType=NewAcct. They charge the absolute minimum in fees, and it mirrors wht the S&P 500 does (the 500 largest publically traded stocks in the US). It will go up some years, it will go down others... but if you buy and hold, you should have annualized gains >7% over a 10+ year time frame.
As to what you can/should do now - As I've said, the most important thing I think is for you to make professional connections and be as employable as you can following graduation. Right now, it's kind of a tossup as to what you do with your extra money. If you paid down your 6.8% student loan you'd get a virtual 6.8% return, which is overall pretty good. But, I think you can do better putting that money into your IRA and letting it compound for a few decades. In 2014 you are permitted a $5,500 contribution. My advice is to pay enough to your student loan that the principle doesn't increase and maybe goes down very slightly (e.g. pay slightly more than the annual interest), and then put the rest into a Vanguard 500 IRA. Since your tax bill will be miniscule already, I'd recommend the ROTH IRA - a traditional IRA gives you a tax break now, but you wouldn't likely utilize that to it's full extent, and I'm not sure you want to get into rolling over traditional IRA funds into ROTH IRA funds just yet...
Just by being here and being aware you are on to a GREAT start. Keep saving, make yourself marketable and you'll have FI well before you turn 40.