You can tell when they're full of wee because they go kind of hard & lumpy. Don't change at every wee, they dribble little bits out all the time. Just do it when the nappy feels heavy or hard or there's poo. Disposables have a layer to keep the wee away from the skin so unless they're saturated the baby won't feel wet.
I don't even change after every bit of poo but only because she sharts constantly! I only change when it's a proper big load if poo , otherwise I'd be changing constantly too.
Asdas newborn nappies are good & are on offer at the minute in their baby event.
Every MW / HV I came into contact with said 6-8 wet and dirty nappies a day. This is what i got through with DS - a dirty was changed immediately, and I took a wet nappy to mean one that had a spongy bit at the front (so actually multiple wee's as they do lots and lots of little trickle sized wee's).
Unless saturated or dirty a modern disposable nappy will keep babies skin clean and dry.
At this age, I changed at each feed (we were feeding every 3 hours) or when I smelled poo. I also did this thru the night until a friend told me to stop it! If you do it at night if there's poo and then every 4 or 5 hours during the day, that's plenty.
Whilst we're sharing info, has anyone told you that vests can be pulled down the way as well as over baby's head (useful for huge leaking poos you don't want to drag over the baby's head!!).
In hindsight we changed DD's nappy far more than necessary and we only got through 12 a day! You must spend your day changing nappies! It does get better though OP, at 14 months we're down to 5-6 a day usually.