filtersl ike your marineland aren't used in saltwater. They turn into nitrate traps similar to canister filters. Your rock will filter the water for you. In terms of base and live rock, all the rock you get will become live after the cycle, so pick whichever you like. The general rule of thumb is 1 lb of rock per gallon, same goes for sand unless you want a deeper sandbed, which is your choice really. In terms of sand, if you are looking to save money you can simply buy pool filter sand.
In terms of cost you, that is a general question. Will this be a FO
system or a reef? If it is going to be a reef, then you will have a heavy investment into the lighting. Biggest mistake I see in this hobby is people buying coral and anemones expecting it to survive under the stock lighting that came with their tank. Sadly, it just doesn't work.