quality lab blocks (Harlan Teklad, Mazuri, Hagen Nutri-blocks,even LM Animal Farms, etc...no Sunseed or Kaytee or Reggie Rat) are the best choice being a complete nutritional diet, then you supplement with veggies, some fruit, some protein.
Forbidden food list (old but it has most things)
If you cannot get your hands on quality lab blocks (Mazuri is sold out of Petsmart) then google "Suebee's Mix" and its a rat mix you can make up yourself. Very important is the dog kibble...has to be low fat, low protein, there are suggested varieties there.
Fresh water is a must, and I change my rats water everyday and scrub out the water bottle often.
Bedding - as was mentioned previously, NO pine or cedar, aspen shavings are fine but make sure they are a quality brand, as some of the cheaper ones are dusty. You might also want to freeze your bedding for 48 hours before using it to kill any parasites (lice/mites) that might be hitching a ride. Other people use Yesterday's News Litter (I use it in my litter pans), Carefresh, Cell-Sorb, fabric like fleece (fleece is good because there are no strings for a rat to get caught up in and injured), etc.
Your rats will need a hidey house (a small box is fine, and there's plastic igloos, snap together houses (snap-inn's in Canada/UK, and waffle houses in US), etc, and a hammock (you can buy them from ppl who make them online, pick up ones for ferrets at petstores or even make your own cheaply and easily.
Wooden bird chew toys are great for rats. I use wooden ladders to enable them to get to a corner shelf I put in their cages, cat jingle balls, etc.
If your rats are babies its advisable to get a wheel for them (either a solid one or the Super Pet 11" mesh wheels are great. A lot of rats as babies will figure out and run in a wheel, which is very healthy for them and usually makes them happy.
Where are you looking for your rats? Its not advisable to get them from Petsmart or Petco or Petland. I hear way too many horror stories on ALL the rat forums about pregnancies, ill and dying rats, etc.
There are usually a lot of rehomes and oops litters needing homes in most areas.
Lastly, start saving for a vet fund. Rats may seem inexpensive but once they get sick they could cost you $50-150 at the vet easily per visit. I hope not to see you posting that your rat is sick, can't go to the vet, and how can you make them better at home.