Now that im starting to run at my school's gym, I have been running for a total distance of 2 miles (just getting back in shape). Anyways, I run 3 laps and walk 1 until I reach 16 laps which = 2 miles.

Is this a good approach? My goal is to increase my endurance, im not focusing on speed or agility for the time being. And if it is a good approach what should be my increment from week to week?

What you are doing is fine.
Next week you should increase it a quarter mile, with incremental walks in between, and then at the end of the week run the whole thing without walking.
Every week increase the distance a little more, with walking increments. Always end the week with a straight run with no walking (besides the warm up walk of a quarter mile or 5 minutes)
Once you get to a comfortable distance transition over to running the whole thing every time.

thanks for the advice