This is my model for the Marble Run contest. It is block based with pegs on three sides and holes on the other three to connect them. I have made all sorts of types of blocks. It is designed to be used by the marbles sold on the Bambu Lab website which are 14 mm in diameter. The blocks have decent clutch power so it will be able to connect firmly.

The blocks included are but not limited to:

Basic block

Funnel

Tunnel

90 degree tunnel

4-way tunnel

6-way tunnel

open versions of the tunnels

gate

switch

trapdoor

elevator

45 degree brackets

and more

To make the elevator, add the elevator bottom, add the twist bottom part, put normal twist pieces on top to desired height, add the top twist part, add all the basic elevator pieces onto the base elevator piece, slide the corkscrew twist thing inside with the extended part going into the holder, add the top elevator piece on with the extending part of the corkscrew going into the mount, put on the knob. It is recommended that you put on super glue when connecting the twist things, but is unnecessary for the blocks unless they are loose.

If the pegs won't go into the hole, you can use a utility knife to shave the hole large or the peg smaller. 

Printing parameters:

print with tree supports,

Don't print supports on the bottom holes as it will be hard to remove without tweezers,

and Gyroid for infill, but it doesn't matter too much.