Hated Dr Brown; we used Tommee Tippee

No a bottle warmer or sterilizer is not necessary at all!! It’s just another thing on the market to make money. Boiling water in a pot and putting the pieces in to sterilize is just fine and just as effective. Warming a bottle in a warmer or in the microwave is also not a great idea as it can create hot spots in the bottle. You can simply heat up water in a pot and then put the bottle in there for a few minutes to warm it up if you feel the need to. Bottles I recommended are MAM. They resemble the mothers breast the best.

Dr browns bottles and assortment