You should start her out on whatever food the breeder was feeding her. If you want to switch foods for any reason, do it gradually to avoid tummy upset. Start with a small proportion of the new food and increase it over a period of weeks.
As for specific brands, it will depend on budget, availability and any special needs for your pup. We are down to one smallish dog and I recently switched from Purina ProPlan - which is a pretty decent kibble - to a fresh commercial food.
I agree, unless the breeder was feeding something extremely poor quality or dangerous, stick to the same diet for a few weeks while your puppy is settling in, so they're dealing with one less big change during that transition. My breeder gave us a small amount of the food she was using when we picked our pup up, and your might do the same or just give you the name of the brand/formula they use. There's no such thing as a single best food for every puppy/dog in every circumstance, so if the breeder's food is working really well for the puppy and suits your budget and lifestyle (eg if the breeder is spending two hours every weekend cooking and blending a complicated home-cooked diet that might not be the something that works for you), you can absolutely stick with it until it's time to transition to adult food (if it's not already an all life stages formula)! Otherwise, as RonE said, slow transition to any new food you want to try is key.
I intend to transition my puppy properly to a new food but I don’t know what to go with. The breeder is feeding a food that is very expensive so I can’t stick with it. It’s a food sold in a pyramid type private way and I won’t continue with it. I was looking at Blue Buffalo puppy food, do you think that’s a good one to transition too? I don’t mind spending a bit more for a good food but I just am not sure which way to go with it.
Ah, yeah, that's absolutely one of the situations where switching foods is absolutely understandable. I cannot in good conscious support any MLM schemes either, even if the products are superior to other options on the market (which they almost never are).
There's a lot of reports of dogs not doing well on or just not liking Blue Buffalo. I only fed it once (the Wilderness line), eight-ish years ago when my older dog was a puppy, and it remains the only food he just wasn't enthusiastic about eating, and I haven't tried it again since. I don't think it's an inherently bad food if your dog likes it and does well on it, but it's also pretty hit or miss. You're not doing any harm if you want to try it, just giving you my own experience!
Fromm has a very good reputation, and has grain-free and grain-inclusive options to chose from. I liked it quite a lot when I was feeding it (my poodle was an adult by then). I also quite liked Annamaet, but had a difficult time sourcing it locally - you may have better luck going through a web retailer like Chewy. Purina Pro Plan is a less expensive, grain inclusive option that works well for many dogs and is absolutely a solid choice as well. I haven't tried it personally, but if you're a Costco member, their Kirkland Signature line also has an excellent reputation and is definitely among the best value options in terms of the quality you get for your price. Whatever you choose, let your puppy tell you if it's working for them. If they're not eating enthusiastically, having difficulty maintaining a healthy weight, developing an unpleasant odor and/or stinky, sloppy poos, and/or have a lackluster coat, it probably just isn't right for your puppy even if it's an excellent product that works for other dogs.
I used to feed my past pups Fromm and they did very well on that (all their lives). I started feeding my current pup Acana, less expensive sister brand of Orijen, and my pup is also doing very well on it.
Another one I really like (I use for treat training) is Nutrience Infusion.
Fromm and Nutrience infusion includes grains, Acana has a new line which includes grains, but mostly it is grain free.
Best to do your own research about whether you want to feed grain free or not, there's A LOT of info out there, if you want the info I have, shout out.