If budget or environmental is an issue then it can be reduced hugely.
Car seat if you have a car.
7 vests
7 babygros
4 sheets
Nappies ( if going with reusables do not buy a big expensive kit you do not need one you can get everything you need for about £90)
4 blankets or sleeping bags
I never bothered with those thin cloths and just got a stack of flat terry nappies and used those instead the bonus is you can also use them as nappies in a emergency or as well they last longer and are cheaper.
I also had reusable wipes but a small packet of disposable ones are handy for when out and about.
Thick sanitary towels
2 pairs of reusable breast pads
Bottle of witch hazel
Somewhere for the baby to sleep I wouldn't bother with a Moses basket ikea do a very cheap cot its about £30.
If bottle feeding then bottles steriliser formula, again avoid buying a big kit as you may not get on with the bottles and they can be over priced.
If bf with occasional expressing the bottle can be sterilised in any tub you want with cold water and a tablet so no fancy steam machine needed try to avoid buying a pump in advance you can borrow one from most sure start centres.
Baby baths are pointless bits of plastic unless you have a reason to need the baby on a stand at a certain height but often sinks work just as well as do adult baths.
I found a bouncy chair (think it was about a tenner from amazon) very useful as I bath all mine with me in the tub and it was handy to have baby in one whilst I washed and so I could climb out. And just to use about the house when I wanted to put the baby down.
Never bothered with a changing mat as laps are fine but a fold up one is handy for when out.
You do not need special baby towels or flannels or many of the other things that you already own but in adult size or pram shoes or anything you look at and think "what's the point"
If a changing bag is expensive enough to make you fret about losing it then you do not need it.
A method of transport for the baby this does not need to cost huge sums of money nor does it need to be a trendy brand.