first thing i can tell you is use screws, not nails when building. also you first have to figure out if your going to float the rail or will it be mounted in the ground. if mounting in the ground figure out how deep the dirt is first and then start making your plans. if your floating it the first step is to figure out what you will use to float it. you want to do this to be able to build the framework around the floats.
as far as surface there are many many types of material you can use. Trex, benderboard, pvc sheet, pvc pipes(old school and dont last long but still works), rfp? the list goes on. anything that is somewhat slick will work. ideally you want something that will be thick enough for you do be able to countersink your screws so they arent sticking up