Anything that slips on and off one shoulder really easily when breastfeeding is good, and is comfortable for both day and night. I had an emerg c/s and found that with limited movement singlet tops with narrow straps were really easy to manipulate whilst holding a squirmy thing and attempting to get them to attach correctly at four am. I just wore them with drawstring or elastic waisted cotton pants and found that they were fine against the wound. You can also get nursing bra style singlets which are not uncomfortable to sleep in. You don't have to wear nursing bras (I don't because I have always hated wearing bras and still do), but I think a lot of people find them more comfortable if they get engorged and pressure against the breast helps leaking when your milk comes in. I just use a tissue myself, but I don't leak much.

A couple of pairs of big cotton nana knickers are essential in case of a c/s - I normally wear hipster/ boyleg style undies and needed to send someone out to get a couple of full briefs because the band on my normal undies rested against the wound.

You probably already know that it can take some time before your tummy goes back to normal, and if you've had fluid retention it often gets MUCH, MUCH worse in the first week or so after the birth - my legs looked like sausages for about a week and everything swelled up down there from a long pushing stage (didn't get to push him out but got pretty close!) so really loose comfy stuff is essential.