With more piers (or posts, pillars or how you call them) you will need more tracks for bridges immediately.

I made some for my sons.

There is also an extra long track rail that is not available in the original GraviTrax set that covers 4 bases (!)

Links to my other GraviTrax compatible parts: Curves, Straights, and Joins: https://www.thingiverse.com/thing:2738494 Pendulum ball starter: https://www.thingiverse.com/thing:2738573 Magnetic cannon: https://www.thingiverse.com/thing:2738601 Bridge piers: https://www.thingiverse.com/thing:2738439