The essential treatment to diabetes is the insulin treatment. In cats, as with many medications, there are a selected few treatments that are effective. The benefit with choosing a more expensive insulin (i.e. Glargine) is that cats can have a remission of their diabetes where treatment with insulin is no longer necessary. This works approximately 90% of the time with Glargine (i.e. "Lantus") and can be observed within 3-6 months after starting treatment. However, it is one of the more expensive therapies, but hopefully the expense pays off over time with not having to use insulin for an extended time. The only other insulin approved for cats is called PZI - it is more affordable than Glargine.
A more affordable insulin type that is not technically approved for diabetes in cats, but can still be used off label is either Novolin or Humulin. Novolin is a Wal-Mart insulin used for people. The reason it is not approved for cats is because we have a difficult time regulating diabetes with this insulin. However, it is a cheaper option.
Regarding the food, you want one with a carbohydrate content that it is <20% (this is on a metabolized energy content, but you would just want to look at the number). Some pet food companies do not put this on the label, which is frustrating, and you have to call the company and ask. A dry food is better, but all over-the-counter options will have carbohydrate content above the recommendation. Some are just worse than others. Fancy Feast, for example, will be above 50%. Some cats are able to go into remission with brands like EVO, which is more expensive than Fancy Feast, but less than the prescription diet. If Bugsy enjoys people food then you might be successful with a balanced raw diet that you lightly cook, like Nature's Variety organic, raw frozen diets.