I have a breaker that tripped this morning. I unplugged everything and turned it back on. It stays on for awhile and for no reason trips again. Lights all work fine without tripping the breaker (immediately anyways). I tested the voltage on all of the outlets and it reads about 120v from hot to neutral on all of them. However from hot to ground varies from room to room, anywhere from 30 to 60's and neutral to ground reads anywhere from 15 to 30's voltage. I counted for the first time and realized I have 10 lights and 12 outlets off one single 15amp breaker. Is this too many? What does the voltage indicate and how do I trace it to the source?

Sounds like an open neutral in part of the circuit, and/or a short.

Need to open each outlet, light, switch, and junction box to check for loose splice, short, etc.

Start at the beginning of the circuit from the panel, trace the cable and find each junction box.