Gear ratio is very much personal preference, motor and battery specific. Sorry, it isn’t much help!
When you know what speed/torque you want use an online eskate calculator to work out the ratio and ensure you have that overall ratio.
Best to make the design such that you can adjust the ratio after building by a simple modification, ie change one gear. Then you can fine tune it later without having to start from scratch.
The gear profiles (module etc) have pros and cons, like noise, strength and efficiency. Best to have a look around if you haven’t already. Bear in mind you could buy gears off the shelf in metal. Might be cheaper and less problematic than 3D printing; just thinking out loud.
Daval gears is a supplier in UK that comes to mind, use the knowledge on their site/catalogue but they probably wont sell 1s and 2s.