I feel like it's worth mentioning here:

DO NOT MIX BLEACH AND AMMONIA. You can die.

No stupid questions should also mean no stupid answers imo. You’ll need a sponge, a hard scrubber of some sort (I think steel wool fuck your bathroom up). Grime remover of some sort. Soap will work but some stuff is just too tough like hard deposits think “Calcium Lime Rust” for this. Whatever you do DO NOT mix bleach and ammonia, you’ll kill yourself. It’s not too hard to clean overall just a pain in the ass. Keep it clean by doing little bits all the time and it won’t be so bad. I’d also suggest some rubber gloves just because those chemicals will fuck your skin up and whether you like it or not it will get absorbed into your skin

I'm really surprised at how many people have their why not to mix cleaning supplies wrong.

Bleach + ammonia can make chloramine gas by the bigger problem would be making NCl3 and blowing your toilet up.

Bleach + acid(like cleaning vinegar) is what makes chlorine gas that will auschwitz your bathroom.

Bleach + rubbing alcohol actually makes chloroform, which is fun.

Just pee on the stains until they give up and go away.

Big fan of 50:50 water and grocery store white vinegar with a tiny drop of dish soap.

For glass I'll also add a little rubbing alcohol to the above, for heavier grease or spots on glass I'll just use 70% rubbing alcohol

Bathrooms can have a ton of different surfaces, I've had great success with VIM bathroom and kitchen but I'm sure anything branded for kitchen/bathroom will handle sink/shower/tub/toilet well.

CLR for anything involving (Calcium, Lime, Rust) tougher sediment buildup.

I get sponges that basically look and feel like the rough part of Velcro and are thin for a sponge, like the green scrubby rectangles, but superior imo.

When they're getting tired they become my household cleaning sponge and work great! A decent sized brush can be handy, and definitely rags/paper towels for wiping things dry if necessary.

Squeegees are fun, not particularly handy for bathroom cleaning unless there's a lot of tile/tempered glass/mirrors or you like using it to wipe down the shower when you're finished

Don’t buy any of those toilet tank tablets. They often will corrode and wear down the tank valve over time, and your toilet will start to run on its own (or could even break).

At the very least, I'd recommend you:

• gloves - because you'll get really close to that gross shit. You don't want to touch it.
• a sponge - it doesn't need to be new; your old kitchen sponge is enough, just don't use it again in the kitchen. Use the yellow side to spread the cleaning agent, and the green side to remove obnoxious grime stuck to something. (Do it gently, and only with a really old sponge, to avoid scratching the surface.)
• a bucket - mostly to mix some soap and water.
• a dry rag - mostly for finishing/drying. A cringey old shirt that you won't be using again is usually enough.
• toilet brush - don't use the sponge to clean inside the toilet bowl; you'll be spreading the bacteria from your shit and piss to the rest of the restroom.

Everyone has the cleaning agents that they swear upon, so look for something that works for you. For me it's

• alcohol vinegar - to get rid of that brown crust in the sink (water in my city is hard as a brick) and around the shower drain. I usually apply it, wait a few minutes, then use the sponge to scrub it a bit. Then I remove the vinegar with the rag.
• bleach - exclusively used inside the toilet bowl. I squish some bleach there, then scrub it with the toilet brush, then flush it off, making sure that there's no bleach behind.
• disinfecting agent - I squish a bit of that inside the toilet bowl and just leave it there. It smells good, and it gets rid of the bacteria.
• an ammonium-based cleaning agent - I squish it on obvious grime on the walls (except the above), then scrub it with the sponge.
• soap and water - to "wash" the walls with the sponge.
• plain water with some disinfecting agent - to rinse it. Then I just remove the excess water with the rag and let the restroom to dry naturally (with closed doors otherwise my cats will step on the bathroom, step outside, and now I got to clean the bathroom again plus the corridor and furniture).

Important detail: do not mix any two of the cleaning agents that I've mentioned. Specially not ammonium and bleach.

For reference, the disinfecting agent that I use is called "pinho sol", but I have no idea if it's sold outside Brazil. You probably have some similar product wherever you live.

Bleach is awesome! Mix it with some water, use a rag or sponge and scrub. DO NOT mix anything else with the bleach. Bleach is basic, and a lot of other cleaning products are acidic. Mix a strong enough acid with a strong enough base and you get mustard gas. It doesn't smell too great, on top of other issues. If you want to clean with bleach plus something, be safe and buy premade cleaner with bleach.

EDIT: I should also say you can't use bleach on everything, it can damage some things. Always test a small, hard to see area before you clean a surface with bleach. For the stuff that you can't get bleach on, you can use white vinegar or all-purpose cleaner.

Bleach for pretty much every surface compatible with it. CLR for the shower itself (or a bathroom cleaner specifically for scale and soap scum). Simple Green (or whatever the equivalent is where you’re from) for every thing else. Buy a decent non-scratch scourer (or a couple) as well as some magic erasers to help with any scale that’s resistant to removal. Oh and glass cleaner for the mirror and maybe shower. Nitrile gloves never hurt if you’re dealing with heavy duty chemicals either. Keep the bathroom well ventilated and never mix chemicals.

If you have tile in your bathroom, do a test in a small out of the way on the tile when cleaning. That way if it damages the tile you don’t have a major problem. This actually goes for all surfaces.

For the bathroom, I swear by my steam cleaner. No chemicals, just hot steam. If that doesn't get it, vinegar is good escalation. Soak the spots in vinegar and you should be able to wipe it off easy. Maybe screw you shower head off the wall and let it soak over night.

Specifically for toilet bowls, if you find that a stain won't shift even after using a normal toilet bowl cleaner solution and a normal toilet brush, don't try to brush harder as this will scratch the porcelain surface. Also don't try something abrasive like steel wool or the green/blue side of a kitchen sponge.

Instead, what you want to do is dissolve the stain. Others have suggested CLR and that might work. But if not, then you can obtain "acidic toilet bowl cleaner", which contains hydrochloric acid, aka muriatic acid. This will remove most anything normally staining a toilet bowl, but make sure you handle it sturdily and carefully; it can mess you up. Gloves and eye protection are highly recommended, until the bowl is brushed, the stain is gone, and the bowl is flushed. Turn on the bathroom fan or open a window for ventilation during and after cleaning.

In general, for difficult cleaning jobs, don't try to clean harder, but clean smarter. If you're putting your whole body weight into a towel or a brush, there's almost certainly an easier way. Good luck!

One thing I've learned is if you have hard, yellow stains inside your toilet, you can use a pumice stone to magically erase it away. Blew my mind.

What kind of surfaces do you have? For example, I've found CLR is good for grout and tiles, while a basic bleach-based spray is good for porcelain and fiberglass. You can also mix in an ammonia-based cleaner if you want to recreate the Third Battle of Ypres in your bathroom.

It's not the only one you should use, but white vinegar is underrated. It's safer than most options, strong if used right, and deodorizes. You can buy bottles of stronger %s at a hardware store and mix what you need in a spray bottle.

50% or greater concentration of hydrochloric acid, wearing a hazmat suit, spray with standard spray bottle on everything disgusting and let it sit, wash thoroughly with sodium hydroxide to neutralize any remaining acid.

Normally I use a bucket of hot water and mix in a bunch of dawn and use a mop. If it's a particularly stubborn pinesol works fine. A sponge to gently wash the walls too.

Edit: Mr clean magic eraser is great for stubborn need but be careful with it. It's essentially sandpaper. Wear gloves!

I'm not sure the application, but probably fire could be useful. Just being silly. Ignore me.

Have you tried soap and water?

Edit: https://en.m.wikipedia.org/wiki/KISS_principle