I totally agree with Vladina about getting two rats ^^ that is a very important thing. Rats need company. And, it shouldn't be a problem getting two because they are very cheap animals, anyway (unlike other more exotic pets).
1. The staple diet is a good brand of a rat lab block. I'm going with an Oxbow Regal Rat. It doesn't contain fatty foods like the mixes do and rats can't be picky and only eat the things they like. On the side of that main food, you can give your rat veggies and fruits to keep things interesting and healthy. Make sure it's safe for them first.
2. If you want a tame pet right off the bat, get your rat from a breeder. They'll be socialized and used to humans. Otherwise, take things slowly. Bribe them with treats, ect. There are many helpful tips and guides online about taming.
3. Some good rat treats could even BE the fruits and vegetables. Besides that, you can give them yogurt drops, raisins, gurber baby puffs, cheerios, ect. And of course, don't over feed them on the treats.
4. Bird chew toys are great, toilet paper rolls, tissue boxes as hidey homes or for chewing, cat balls to play and toss around with, hammocks need to be in the cage, tunnels, ect.
Do some research and look at the other threads on the forum for more tips. Good luck with your new rattie