I hope this isn't redundant, you haven't mentioned how many firearms you've owned, so I'll assume none in some of the below comments:
One suggestion is to use some of our ammo vendors that advertise here -- on http://www.ammoman.com, both lake city and Q131A 55gr. XM193 is $199 for 1,000 rounds and shipping is free. You'll need lots of ammo!
Read up on the improved battlesight zero, for a carbine like you have, it's the best way to get set up. There are other methods worth checking out -- finding a bullet drop chart for the 55gr ammo is possible and it helps explain why you hit where you hit at certain ranges.
Third, I'm not sure who sells a good cleaning 'kit', I'd recommend a Dewey Rod and bore guide, a chamber brush and rod, lots of 22 caliber patches, and a few bronze .22 brushes. Opinions on fluids for cleaning will vary greatly.
Fourth, clean it before you shoot. Shipping grease and factory guk is in place and doesn't allow the system to work as freely as it should at times.
Fifth, the equipment exchange is your best place for a quantity of mags. A few emails should get you as many as you want of each.
I'm sure you'll get much more advice. Enjoy.
-Dan