I'm going to just go over the specifics of a pet bunny's diet.
Bunnies' rely on hay for most of their diet. You should make sure that they have hay at all times. Some people just put hay in the bowl, but I got a wire ball feeder similar to this. I just stuff that with hay whenever Wafer runs out.
In addition to hay, your pet will need pellets. <- That's the brand that I use. In the past, I also have purchased this, but that was almost $2 per lb, whereas my current brand is about .50 cents per lb. The more expensive brand probably has a slightly higher quality, but not so much that it's worth paying that much more for. Also, it is vital that you choose a brand without those colorful, crunchy things. Those are like lucky charms in a bowl of cheerios. Your bunny will love them and may even neglect the more natural pellets. They're like McDonald's for bunnies, and every hipster knows McDonald's is ucky. ^~^
As with treats, again, try to stay away from fake-y, colorful stuff. Bunny owners often say, the thing you bunny will love the most is homemade. They're going to enjoy eating the packaging more than the actual stuff inside. If you do go the store-bought route, stick to the more natural brands or these great yogurt drops that Wafer loves. In fact, you can even try making your own bunny treats! <- I have made this recipe before, and Wafer loved them. It is a messy recipe, so plan on getting your hands dirty. Also remember that preservatives are not included (and rightfully so) so they won't last forever.
Finally, bunnies should get some veggies in their everyday diet. Many ask if this means that they need to buy veggies for their pet, but the answer is no, you do not. Even though every bunny is different, it doesn't need to be complicated. Some acceptable greens, to name a few, are: lettuce, cabbage, kale, spinach, brussel sprouts, broccoli, bell peppers, sprouts, and dandelion leaves from your yard outside. Just remember to double check online if you're trying something different and to wash everything before you give it to your bunny. If he/she hasn't eaten it in 24 hours, try something else and throw away the wilted vegetable. Again, every bunny is different and probably won't like everything you give them. Wafer, for example, hates carrots but loves broccoli and rosemary. You just have to experiment a bit and find what is you buddy's favorites.