Best way to clean a dirty shower?

Mold- Bleach

Mildew- Soft Scrub

Rust- 40 Grit

Concrobium works pretty good on the mold and mildew. Get it at Home Depot.

They sell this cleaner at the doller store its called Awesome, and it is!

Vinegar and dish soap. Scrub the hell out of it and let it sit for about 10 minutes before rinsing.

You want a cleaner with quaternary ammonium imo. It will penetrate deeper and kill mold down to the hyphae(anchoring 'roots'). After that, it's all about moisture mitigation.

What is the shower made of? Some materials can’t handle certain cleaners

I keep a 4 foot boat deck brush in my shower. Scrub a little everyday when I’m taking my shower. Occasionally turn the water off for a bit and sprinkle some bartenders friend, and get after it with the big brush.

Otherwise, whatever ‘the help’ does.

Not sure what materials your shower is made out of, but for tile/grout, I cannot sing the praises of grout sealer enough.

Once you get it as clean as humanly possible (or when it's newly installed) get something like this. It's super easy to apply and cuts your cleaning time down to almost nothing. Think of it as kinda painting your grout as far as adding color and filling in the pores.

We sealed ours right after our master bath renovation... I almost never have to scrub the grout (and when I do, chances are it's a spot that I didn't seal super-well and can re-do to prevent from recurring). Our existing tile floor grout looks like new after sealing and now stays clean.