When getting pellets, I’m sure you already know this, but it’s best to avoid the junky kinds that have seeds/colored pieces/things like that in there. Personally, I use Oxbow Essentials pellets, they have all the good stuff in there. It’s important for pellets to have a lot of Crude Fiber and the Oxbow Essentials have 25%! How old is your bunny going to be? Depending on if he’s younger than 7 months-1 year you could have him on young rabbit pellets could be better.
For hay, I use Small Pet Select hay. They only sell it online but it’s really fresh, good quality hay! To start though, I would get small packages of different kinds of hay. Before I got Alfie, I bought a huuuge bag of timothy hay, turns out he’s so picky with hay he’ll only eat orchard grass hay.

Congrats on your new bunny! Would love to see photos when you bring her home

Bunny diet can be so confusing and it’s easy to get overwhelmed by it all. Start off simple. Good quality pellets and hay are perfect for a young bun. Pellets should be plain (no seed mixes or anything like that) A lot of people use Oxbow – I did too for a while. As yours will be a baby, you’ll want junior pellets as they have more protein in them which a growing bun needs. Of course, make the change gradually but you already knew that

In terms of hay, a lot of people reccomend alfalfa for a growing bun BUT if you are giving junior pellets, then you don’t need alfalfa. In my opinion, I wouldn’t use alfalfa at all because once bun reaches full size, you’ll need to switch over and because alfalfa is really yummy, it can be difficult getting a stubborn bun to eat other hays! Timothy hay, oat and orchard are all great hays and nutritionally speaking, they’re all pretty much equal so there’s no hay that is better than another. So long as bun eats plenty of it! I personally use three different hays – I think variety is important because it stops them getting bored and if for some reason, one hay became unavailable (a stock shortage or something) you’ve got other options that you know they’ll eat. I give mine Oxbow Orchard Grass and Oxbow Timothy. Both of which I buy in bulk – I buy 11kg for £58ish which works out as £5ish per kg. It’s even cheaper per kg to buy the 22kg boxes but I think it’d go off before I got through it so I stick with 11kg boxes of each. Of course if you want to try Oxbow, buy a small bag to start with just in case! They have orchard in one litterbox 24/7 and timothy in the other 24/7. I also give Burns green oat hay which they absolutely love but I tend to use that as their treat hay – It’s the one I stuff into paper bags, cardboard tubes etc to get them munching throughout the day as mine actually do the majority of their hay eating overnight so they need a little encouragement during the day. 

For veggies, some say you can start giving them at 12 weeks whereas some advise to wait a little longer. This is something that you would probably be best off asking your vet as so many people have differing opinions. When you do start giving veggies, start off small. Romaine/cos lettuce is a nice one to start with because it’s fairly bland and inoffensive. Start with a small square of the lettuce leaf one day. If no issues arise, increase the amount a little each day. Do this for a week or however long it takes to build up to a full leaf or two. Then start with the next veggie. As rabbits primarily need leafy greens as opposed to other veggies, here are some great ones:
-romaine
-green leaf or red leaf lettuce
-coriander/cilantro
-rocket
-watercress
-bok choy/pak choi
-dill
-parsley
-thyme
-basil
-carrot tops
-kale

There are tons more that buns can eat, have a look at the diet section on here or the House Rabbit Society for a loooong list

You don’t need to go crazy, once you’ve introduced each veggie that you want to try you can give say, 3 or 4 different types per day. So romaine, watercress, rocket and dill for example. Then when your stock of that runs out, choose another 3 or 4 types. Or you could keep one or two staples such as romaine and rocket and vary the other two every week. It doesn’t need to be complicated   My rabbits actually don’t have veggies anymore because of sensitive tummy issues (I’ve spoken to a vet about this don’t worry!) but they absolutely loved romaine and dill. 

Forage! Forage is a great addition to a rabbit’s diet and it’s something I focus a lot on because of the ‘no veggies’ although I think it’s crucial anyway even if you provide lots of veggies. Rabbits in the wild would obviously eat a lot of fresh leaves and flowers but as most of us here have indoor bunnies, we opt for dried varieties! Dandelion is and huge hit for my two lops. I hide it around their room every evening I also use blackcurrant leaves, nettle, echinacea, sunflower petals, mallow, cornflower and marigold. I pick one each day and sprinkle a little on their hay before I go to bed. Last night was blackcurrant leaves and tonight will be sunflower petals I just take a pinch or two of whichever one and put it on the hay in both litter trays. Like anything though, introduce slowly.

Treats!! Treats from pet shops are generally a huge no-no as they often have ingredients that just aren’t suitable for bunnies. You can actually hand feed some of their regular pellets as treats or give an extra piece of veg. Rabbits go crazy for veg usually and pellets so they’ll think they’re getting spoiled You can give small pieces of fruit as a treat but I personally would leave out fruit until they are eating plenty of veg comfortably just to be sure that their tummies will handle it. Small pieces of carrot make a great treat too! As does the aforementioned forage!

I hope this isn’t too overwhelming!

I was given rabbit royale as a first food when I got Luna – it really is a ‘junk’ rabbit food, full of seeds and fattening bits. I feed Burgess – they do a baby rabbit pellet, and a few varieties of adult pellets (eg flavoured with oregano or mint, no added junk!). Oxbow pellets are another high quality brand.

I agree with pretty much everything Sarah said! My bunnies get timothy hay, which I buy in 9kg sacks for £22, and that lasts my 3 about 5-6 weeks. I also top it with various forage, and pure dried grass as a treat too.