Any Electricians? Advice on wire.

Cudascott and leadfoot gave you good information. Is your range cable 3-wire or 4 wire? If it's 3 wire, you Need to run a fourth wire for a ground from the main panel. From the junction box to the garage you can run at least a 1" conduit keeping the gas Line separate. You need two #6 thhn or thwn wires for the hot leads. One #6 thhn or thwn wire for the ground. Mark this one with white electrical tape. The fourth wire will be a #10 Thhn or thwn wire for the ground. You can buy green wire or you can mark it with green electrical tape. This will give you a 50 amp service to your garage, enough for most air compressors a few lights and a receptacle or two. For your sub panel in your garage, a 100 amp main lug, no main breaker will be good. Buy a 50 amp double breaker to use as the main breaker. Do not screw in the green bonding screw in the new panel. The ground and neutral should bonded together in your main panel. All sub panels need to keep grounds and neutral wires separate. Familiarize yourself with your local codes. Some localities get rather anal with their codes. I've been doing this for a living for almost 40 years now. Good luck!