If I were you I would start with what I would need if the baby arrived tomorrow and work from there.
So:
Somewhere for them to sleep. If you're being given a Moses basket then you will need a new mattress as it isn't recommended to reuse them. You can buy online cheaply if you know the size.
Baby grows and vests. Supermarket. Cheap and plain. Lots of if you don't want to be washing constantly in the event of a sicky baby.
Lightweight blankets, cellular are very good. Also muslins. Again, lots of and supermarket cheapies.
Feeing- breast or bottle then go from there.
Baby monitor, not essential but handy.
Thermometer for the room, not essential but again handy and can be very cheap.
Nappies, cotton wool, wipes suitable for newborns if you want to use them. Nappy sacks.
Flannels and towel for bath.
A way to get them home from the hospital, so pram or car seat depending on whether you have a car or not.
Have you bought things for you? Maternity pads, breast pads, arnica etc?