We use kirkland brand formula from costco. It's repackaged Similac. Exactly the same thing and it is less than half the cost. It even comes in the same plastic containers. They just change the stickers. All the other off-brands are likely just as good as any brand name and usually just repackaged brand name stuff anyway.

Filtered water is fine unless you live in an area with lead problems.

And what obscene cost for bottles? We have exactly 4 bottles so far for our 4 month old and they were less than $5 each. And new nipples are about $2 each when we needed to change the flow.