First u need riddillin lol j/p!
New barrel- CP, Evil, J&J depends on how mutch u want to spend. This isn't a necesity the stock barrel is ok.
Hopper- Your defiantly going to want a agitated hopper. I suggest this. Go to xpaintball.com and look at the agitated hoppers. There is one called the, Extreme Rage Overdrive Hopper for $26 dollars. It's a great hopper for the price i have one and it keeps up with the tessy awsomely no problems what so ever.
Air system- I would suggest going with HPA if you got the money, but if not Co2 works just fine!
*New Bolt*, A most need- the stock bolt is ok, but it eats oil like a ***** and it will ware down the inside of you gun. So i would go and get the Shocktech T.E.S super fly bolt. If you don't want to get a new bolt then just make sure u oil the crap out of the stock one. Trust me on that!
Umm i can't think of anything else right now you might want to get a harder and longer spring for more volacity cuz it's kina low.
Well other than that the T.E.S is a great gun and you will enjoy it very mutch.
P.S. if you want later on u can always go and get "The One" Kit a very good investment!
Hope this helped!
Also when you get your tessy go and check out the dragun owners group if you haven't already!