Check out the mediterrainean torts. There's a few different species (hermanns, greeks, russians, marginateds) that are widely available. These all are great species because they are small, don't cost much to feed, and for the most part are tolerant of a wide range of climates. These tortoises hibernate when temps become too low. Russians especially are able to survive (and hibernate) in climates that have harsh winters.
You should also consider redfoots. They are great torts. A little larger than most mediterraineans, but they have been praised for their personalities. They are a rainforest tortoise that thrives in higher humidities, and they need some animal protein in their diet in order to stay healthy. These tortoises do not hibernate.
Sulcatas are also a popular choice. They have good personalities, and tend to thrive when given the proper environment, however they quickly grow very large (some are over 100 pounds and 30" shell length). These tortoises do not hibernate. Like most tortoises, sulcatas burrow. As you can imagine though, the burrow of a 30" sulcata is going to be much more substantial than that of a 7" russian. They are known for their ability to 'modify' landscapes.
Leopard tortoises are beautiful, however I've noticed that many people tend to have trouble with them. They are not as hardy as the other tortoises I've mentioned, and are much more susceptible to respiratory ailments. They can make great pets though, if you really work to provide them with the absolute best care.
So these are just a few options you should research. I'm a big fan of the mediterranean tortoises, simply because they are small in size (which means that you can easily give them plenty of room to roam and burrow...whereas a sulcata would need a much larger yard, and are known for constructing huge burrows). They are also much cheaper to feed, and if you have good plant growth outdoors, usually will not need much supplemental food (if any). My next personal favorites are the redfoots, which I hope to work with in the future. These slightly larger tortoises have beautiful markings.
It's all about preference. I'm sorry I don't have any real numbers for you, however for my four russian tortoises, on average it probably costs about $4-5 per week in food during the cooler months (which means all but two or three summer months here). In the summer they tend to eat far less store bought produce simply because they have access to dandelions, plantain, and other naturally growing weeds in my yard.
Good luck with your tortoise endeavor!