Firstly, when it comes to quantities, that’s really easy: you have the area and you have "height" of every layer, so just multiply those two numbers and add 10-15% because you always lose some material. Now when it comes to how thick layers should be that depends really. You should excavate fertile layer of soil (at least) because this layers contains organic ingredients which decompose and then you get a "hole" (well many small ones actually) which then causes slab to sink. Now once you have removed the soil it would be a good thing to compact it a bit with hand compactor or something. If you have time maybe it would be a good idea to leave it be for a few days or a week (if possible) so it would naturally settle but there's not much to settle anyway so this isn't necessary. Next step is compacting crushed stone. Now like handyman said plate compactor would be the best solution but again we can work our way around it ;) .Pour thinner layers of gravel and use hand compactor (sometimes when I don't have any compactor I even use wooden mallet).You can pour some water between layers in order to compact it better. Do this for several hours (with brakes of course during which gravel will settle).When it comes to thickness 10cm or 4 inches should be more than enough. If you don't think that crushed stone is compacted enough you can do one more thing: mix cement with a lot of water (I’m not sure that it is proper English translation but I think that mixture is called cement milk) and then just pour it all over gravel. This will create pretty strong layer for your paving. Now comes the next step where you should make a choice: either you can make a sheet out of fine sand, or if you want to make it bullet proof you just pour 2-4ches thick concrete slab. Make sure to put some reinforcement meshes. Now if you do this I think that there is no need to pour cement milk over gravel. Then you make sand sheet and finally lay the pavers. Slope should ALWAYS take the water away from the house. It should be somewhere between 1-2% meaning: for the length of 1 meter there should elevation difference of 1-2cm (1/100) (convert it into inches, feet).Also, keep in mind that final level should make sense; what I meant is that it should be leveled up either with manhole or slab (lower ones) around your house. But keep in mind that your pavers can not be higher than top of the manhole (if paving doesn't end before manhole....that's really important. Also, what I forgot to tell you is that if you pour concrete slab under pavers you cannot easily remove them then you need to repair some pipe (if any are under paving); you must demolish this slab. If you have any further question just ask.