Well, a "good" gear ratio depends entirely on what you want. I really suggest you answer all questions directed at you in this thread; what speed are you hoping for, what terrain you'll be driving on, etc. You've answered the rest, but the ratio depends largely on what you want to do with your kart.
Generally, for off road you're more likely to want more torque, meaning a lower top speed, but still, you'll have more fun being pushed into your seat and having a top speed of 25mph than needing a push to get moving at all and have terrible acceleration, with a top speed of 50.
I don't know about commercial karts, but is it worth asking the rpm of the engine? Would it be the stock 3600 or have no governor and therefore rev higher?
It really isn't as simple as asking and leaving a picture, expecting an answer. I also think it's kind of off-ish to effectively say no to someone trying to help you in their spare time.
