Ok, I wana get a gauge to tell me when my battery is going low. now would I get a volt gauage or a amp gauge?

A simple volt guage is all you need. If you want ultra accurate measurements, run the pos and neg wire feed for the guage directly to the battery. You can hook it up just about anywhere you can find 12 volt and ground, but the reading might be off a tenth or two because of voltage drop. You could use your cig lighter wires for simplicity i suppose..