Use a softer toothbrush than you think is "soft." I got turned on to Quantum super-soft toothbrushes from my dentist and now I special order them from Amazon. (
One buying option.)
A lot of so-called soft toothbrushes will irritate your gums if you spend long near the gumline, causing the exact gum problems you want to avoid. Remember: what feels like it's scrub-scrub-scrubbing your enamel nice and clean will hurt your much more vulnerable gums in the process.
With ultra-soft, I'm able to gently brush at a 45-degree angle for a reasonable while, getting just under the gumline and making everything super nice and clean up there. Since I moved to this brand and went slower and angled with my brushing, all of my checkups have seen improvement. (And they weren't
bad before; I'm moving from "okay and normal" gum territory to "super healthy gums!" by now.)
Add in daily flossing before I brush, and regular cleanings, and my teeth are doing better. And I speak as someone who inherited shitty dental genes from my dad.