Prices on every item is different. See the search bar at the top? Enter an item name while the scrollbar says user shops. The price for that one will come up, cheapest to the most expensive. You can also check non-user shop prices by clicking on the shop list on the navigation bar under Play. Each food is different as well, so, you just have to buy what you think is at a good price for food. XD Candy pizza is sold for around 200 Tu in the pizza shop in the shop lists and it fills your pet up 30 points, so I think that's the best food. Some food items fill your pet up 4 hunger points and others higher. They're all different, but when you view them in your inventory, it will tell you. Pizzas tend to fill your pet more. I do know a good newbie guide, but it's a little outdated as it's from the first version of Rescreatu. The person who wrote it is Geonightrose who is a very experienced member of Rescreatu. ^^ If you need anymore help, just Rmail me. You can Rmail people by clicking Rmail under Community in the navigation bar and clicking compose. Welcome to Rescreatu~!
~Pet
EDIT: Whoops, forgot to post the link. XD
http://www.rescreatu.com/blogs/viewblog/1/6595.html