I would say just go with prefabs plus a bit of decoration to make it look like you put some work into it. Unfortunately, in my opinion the only decent prefab supports are the "single-pole" and "complex" ones. The other ones have weird connectors that are no good for arrows and have weird bracing angles that make them no good for B&Ms
However, this doesn't mean use *only* prefabs. You're going to need a few "real" supports, I'm sure, if only for issues regarding pathways or other track.