There are lots of different types of mulch, mostly Wood chips, sugar cane and straw. The best kind of mulch is none of these… it’s leaves!
Leaves will create organic matter as they break down, they won’t block water from getting to the soil and they are in plentiful supply!
They also make an excellent addition to your compost pile.
For compost, I like to layer a wheelbarrow of leaves then a few shovels of manure (chicken, cow or horse) and then another wheelbarrow of leaves, etc, etc
Each autumn there is an abundance of leaves. I collect from my property (which has a lot of deciduous trees) if you don’t have deciduous trees there are always people throwing away leaves in their rubbish bin.
I like to feed my beds every autumn (so they are good to go by Spring). I feed my beds with a light layer of finished compost and then mulch heavily with leaves. Job done!