Hi! When I was in Tbilisi, I used https://hire-auto.biz/en/rent_car/georgia_tbilisi to rent a car. Great selection, reasonable prices and nice service. Their website is easy to use and the staff is professional in helping with car selection. I personally chose a long term auto and everything went smoothly. The cars are in excellent condition and there were no inconveniences. Bonus - there is an option to return the car in another city. Recommended!