I took a look at thingverse and couldnt find a good set of gears.
You weren't looking very hard then.
For gears you need openscad and one of the MANY customisable gear .scad scripts

There are a bunch of customisable files that use the thingiverse built in customiser.

Go have another look.

Or make your own with openscad. It's one of the easier things to script.

But saying there are no good gears on thingiverse is just contrary to the facts :-)