I've got straw down under the perches so it's easier to get the poo out but that's it. they tend to spread it all over the place. I just keep throwing in more straw until midwinter. Then I shovel it all out in the spring. I've had it this way for almost 3 years on with no problems.
if the floor is inside, i would recomend putting @ least shavings or straw @ the least. no benefit to the birds, just easier for you to cclean. if dirt is outside and they go into a house like mine, i would only put like maybe a little lime or a small layer of straw but remember that it will soak up everything and you have to clean it faster or sooner because of rain andd what not
If you get cold winters, put shavings (or whatever) down to keep the birds warm when they're walking around on the ground, as hard bare ground sucks a lot of warmth out of their feet.
If your soil is real clayey or gets very packed over time, it is also worth putting down some sort of bedding, because it becomes real hard to clean the poo off that (whereas if your soil is very loose and sandy, it may not be a problem)
I suspect that as you have chickens for a while you will end up determining for yourself what you need to do in terms of bedding to make the coop as easily cleanable as possible
Also make sure you've done some sort of predatorproofing to prevent things from just digging under the walls and getting in to eat your chickens -- either bury wire or something 18+" down under the coop walls, or run a heavy gauge wire mesh apron out 2-4' on the ground.