I was hoping to get enough tax return this year to make it into a proper room. But until then, the money just isn't there.
Like I said, it should be fine for storage this winter. I'm just keenly aware that drastic temperature extremes such as dipping into the 30's and then in the dead of summer rising into the 100's has physical affects on plastic and paper products. Have you received a package in the mail with something like a game in it when it is really cold outside? Even though there isn't any perceivable moisture and the contents just appear to be cold, take it inside the house and see what happens. Immediate condensation. I've seen many steelbook DVD, Blu-Ray and video game cases that are rusted not because they were directly exposed to water, but simply because they have experience changes in the temperature like I listed above. The same thing will happen to the connectors in systems like NES, SNES and Genesis.
Again, should be fine for one winter especially this (so far) mild one we are having. Not knowing the layout of your garage, but I assume it already has 2X4 studs on the wall. You can go to a discount lumber or home store that sells seconds (cheaper, not perfect items but still good) and get rolls of insulation or even "blow-in" insulation.
As for drywall, all you need to work with it is a measuring tape, pencil, ruler/straight edge, hammer, drywall screws and a good utility knife. Measure, draw lines with your pencil and then use the utility knife to slice into the drywall. Once you have a straight cut you want, cut into it again deeper using the groove you already made to guide you. Once you are most of the way through, you can just bend the drywall. The paper backing will hold it together but break the inner material. Then just slice along. It's really pretty easy and not as daunting as you might think. You can then either tape & mud the joints where the drywall meets or put up inexpensive paneling.
Get a section of remnant carpet on the cheap from a discount store, lay it down and just trim it with a utility knife to get it where it looks decent and doesn't stand up around the wall.
These things alone will really help maintain a safer temperature range. If the garage is attached to your house and not a separate one, running a duct extension from the closest vent will really help.
We want pics though after you are all done!
A couple hundred dollars and you will have an insulated room.