Gosh, I never brought anything except a muslin cloth, a few wipes in a zip lock bag, two nappies, and a few nappy sacs, tiny sample tube of bepanthen, and a bottle of volvic water for me.
I never needed a change bag, just used my handbag. Always wore a scarf for covering up for feeding. I wear scarves anyway, so that wasn't new.
I wore baby in a sling.
I breastfed. Kept spare breast pads in my bra.
I used the old nappy to wipe off bottoms, and used a wipe to clean. Muslin squares can be used for a change mat if your coat won't do, though I could change babies on my knees mostly.
I put the new nappy under the old one and wrapped the used wipe up in the old nappy and strapped it up into a ball: then used cream, then strapped new nappy on. Never had any mess as the new nappy is under the bum acting as a change mat iykwim. It's very quick that way too.
Later when I had a bottle of formula I had it in my handbag also. Had the measured amount of formula powder in the bottle already and made it up with volvic when I needed it.
Don't really get the change bag thing actually! Handbags are perfect. It's not like you're hiking out in Patagonia.
New clothes can usually be bought if a poonami occurs. (Never had one of those)
Bring a few rattle toys, or a spare pair of socks for baby to play with when changing them to distract them, so you can be quick.