Vinegar and baking soda put vinegar in a spray bottle ad a little water spray the shower down then sprinkle baking soda let sit for a little while then re-spray with the vinegar then wipe! Also an sos pad dose a wonderful job also!
Lysol power in the blue trigger spray bottle and magic eraser.
Cut a grapefruit in half and scrub with kosher salt.
Wet and forget shower for a no scrub cleaner. Use 2x a week until clean then once weekly to keep clean.
I use a vinegar gel.
Once the shower is clean, a quick wipe down with lemon oil will prevent the build up from coming back. do it once a week when you clean the shower.
Use a mix of warm water, baking soda and vinegar to remove the soap scum. The easiest way to keep a shower clean is if you install the wand shower head with the hose which you can remove and use that to spray down the walls before and after your shower.