Just getting our crib and cot bedding organised - am I missing anything or is there anything on these lists you wouldn't bother with?

Crib (first few months):
- new mattress
- fitted crib sheets x2
- baby sleepsacks
- lightweight/breathable blankets
Do I also need waterproof sheets/liner to protect the mattress?

Cot:
- new mattress (with waterproof and breathable cover)
- fitted cot sheets x2
- breathable bumpers
- continue to use sleepsacks/breathable blankets as above.
Again, do I need an extra waterproof sheet as well?

I'm a bit confused by whether adding any kind of mattress protector will impede the 'breathability' of the mattress; so any thoughts would be welcome!