Personally I only use water for the first few months, as long as possible really
I bath my baby every day - even if it’s just with only water - it relaxes her so much and she sleeps so much better! I use Aveeno Dermexa and it’s been great!
I’ve been using breastmilk in baths twice a week and wiping with a cotton pad and moisturising daily since 3 weeks as my LO got really bad cradle cap. Used shampoo once or twice using cotton pads but still haven’t used baby soap
I took him to the drs when he was around 3 weeks for an unrelated issue and the dr asked how I was bathing him and I said just water and she told me we actually advise people to use a non fragrances body wash as sometimes the water can be harsh if you live in a hard water area and then moisturise them at every nappy change (which I thought was a little excessive). So he’s 5 weeks and I’ve been bathing him maybe 3-4 times a week, most of the time it is with just water, like a little freshen up. I use Childs farm unscented range which is very good.