I picked up a wall thickness gauge from Premier Gauges that has worked out really well for me. I'm a lifelong tool junkie and I gained an appreciation for quality tools from my dad, so this thing checked both boxes. The scale gives me a direct indication of how much needs to be removed from an area to even out the wall thickness, so it's easy to zero in on the thickness. I've been rough turning a bunch of blanks and I'm able to get things a lot more even using the gauge. Granted, there are lots of ways to judge wall thickness, and I've tried several different techniques, but this was the first that gives me a visual indication that really helps. Presumably, I'll learn to judge wall thickness as I gain more experience, but in the mean time, this has been quite a help. The gauges aren't cheap, but they're made very well and I consider it money well spent. FWIW, I have no involvement with Premier Gauges other than being a happy customer. Russell Green is the very cordial owner and great to chat with if you call. I like supporting small companies that have good products, and I'll be buying more tools from Premier as finances permit.
https://premiergauges.com/ols/products/premier-gauge-large-prm-gg-lrg1
https://premiergauges.com/ols/products/premier-gauge-large-prm-gg-lrg1