Okay, I’m going to be lazy here, amendments are up to you and your situation, in urban environments the smell of manures can be a problem, composts would probably work better. For me I can’t come up with enough compost to fertilize a potted plant. I do however have access to a decent amount of horse manure. With manure you are going to get seeds so there will be lots of weeds. I personally do not totally condemn the use of chemical fertilizers if they are needed to make the balance right. Using manures may not always create the proper nutritional value for your plants. Saying all of that I would still try to stay as natural as possible but sometimes we may need to do what we need to do. With compost it would be about 2 inches per bed, don’t worry about the paths or the borders. I put about the same amount of horse manure on the beds but don’t have scientific proof that is the right amount.