How many gauges can you have? Go on ISSPRO.com and look through their catalog.
Here is a good video of some options and what he looks for from them.
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Big thing about gauges that hasn't been said, is that you have to know what you're looking at.
I don't place much value on an ammeter. Unless it's using a shunt, they're usually not accurate and can be dangerous. I can diagnose most charging system issues with a voltmeter.