Hiya, cordyline, welcome to the site ;D
Inky, our paths are 18" between beds with a 2' path between, bads are made with old pallet wood, I think there are pics in our gallery..good luck with your growing ;D
we filled them with whatever we could get hold of, card on the bottom to stop the weeds, a mix of old leaves, grass cuttings, soil from wherever and rotted horse muck..it's done us well, all the compost from our carrot beds etc gets added each year with the contents of the compost heap, we even get all the grass cuttings from our neighbours' lawns ;D