I have 1 of each (TT/Dr Brown/Hegen/Avent), baby prefers Avent. I use 4 bottles for newborn stage, all slowest flow (do note for Avent, you have to purchase size 0 seperately as the one that comes with the bottle is size 1).
As my baby is fully bottle fed, 4 bottles is enough as I wash every 1-2 feeds. If intending to latch most of the time, 2 bottles is good enough. For teats, just get the same amount as bottles.
Teats don’t have to upsize so quickly especially if on bm. Just buy as baby grows.