I keep mine pretty slimmed down and close to the default.
My most notable addition is "Situation" under "Biome", to help know when to run science experiments, and I added the "Critical Thermal Percentage" HUD in the middle because my shuttle is thermally limited on ascent and sometimes re-entry too. I sometimes add a few more parameters to the orbital section too. But if I want more detailed info, such as burn time for manoeuvres or radar altitude for landings, I use the KER window.