Straw with bark chippings is fine, if you are worried about it making the soil poorer just add some nitrogen fertiliser.
I've tried every mulch existent, I think, and the honest truth is that just using whatever you can get easily and cheaply and you can put to a pretty good depth is best.
I find 1 cm not nearly enough, I use between 5-10 cm. Anything less the weeds will grow straight through.
Although gravel and the mineral mulches look great for a couple of years, they do start to look tatty after a while so still need refreshing on a fairly regular basis. And as a pp said, they add nothing to the soil (and are pretty much impossible to take off after, so you end up with stony soil). I do use them in pots, as they look much more polished and I am likely to change the whole soil every year.
I am currently using fresh shredded prunings (well, we actually chopped down lots of trees and shredded what was left over after we separated what we can use for firewood) and it's working really well, so if you know a gardener/tree surgeon who might have lots to spare that could be a good solution.