You can get a green tank from Crossfire in 68/3000 steel, or just take any tank and put a green cover on it. Nitrogen is definatley worth the money, and can be found in very functional configurations from $80-$200 that will suit just about all your needs. I personally have almost never been without it. You can go as high as $500+ for it, but really there is little advantage at all. Tanks come in 45/47/48, 68, 88, and 114 cubic inch sizes. The shot count is only a secondary concern (unless you're a back player that is) to how the tank size feels to you in terms of length and balance. Go with what is comfortable.