Position the clutch either way so the sprocket lines up with the rear sprocket (or the jackshaft sprocket).
A baja style minibike with 18 or 19" tires comes stock with 10:1 gear ratio with your typical 5-6HP engine.
Every minibike I've put together used a torque converter and wheelied dangerously (how i like it). So my opinion may not be best for what you like.
Tire size, Engine size, and total weight of bike plus engine plus rider... These will be needed to get a personalized recommendation for gear ratio. Plus where do you ride? Streets? Offroad? Do you start and stop often? Or do you take long cruises on country roads? Do you like to cruise at slow speeds?
If somebody asked me what size shoes are good for guys, I'd say around 10.5. That will work for some, but obviously not the right question to ask if shopping for your own shoes.