Congrats on getting your new printer. However, if you heard that the printer works best using Bambu filaments on default. Hang around here longer and you will find that is categorically NOT the case. Unless you have the AMS option which provides for RF tag identification and the spools fit perfectly in the feeder, there are no other advantages to Bambu filament but many disadvantages.
Another community member has posted here with the exact same out of stock challenge. Here is that thread, you may want to peruse it. Get Refills and Spools separately, or jump ship to Other Brands - #7 by Olias