Hello, Scott, and welcome to the forum.
We use a voltmeter for our trailer plugged into a 12v accessory outlet. Knowing the battery voltage, and charging voltage, is an easy first step, very inexpensive, and an order of magnitude better than the (virtually useless) battery level lights.
For the fresh, grey, and black tanks there are level indicators that are better than the factory ones. Some of those are expensive and some folks report that they get fouled and may not be much better than the factory indicators.
You'll probably hear from folks on this site that have better monitors and what their experience has been.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.