I suppose it depends on how bad it is.
For me the spray would be the outside, making sure you get around the back. The harpic inside. You might find a dettol spray might not be enough to remove some dirt.
For the bath and shower I’d use bathroom specific spray for soap scum, limescale, mould.
I have 2 bathrooms, one en-suite with no window and broken fan so I worry about mould. I use a general soaps scum spray and make sure I use a good black mould spray once a week, Bam is good.
The toilets I clean the outside with antibacterial spray (Dettol is perfect). And I bleach the toilet daily. I’m not a fan of toilet brushes I feel like they are germ breeding bits of yuk.
Bathroom sink, again a good antibacterial spray.
If you have limescale find a limescale spray. My en-suite tap gets bad limescale, I usually spray it and leave it 20 mins before cleaning it off.
If you have a brown toilet it’s probably limescale not poo stains. I always use half a tub of bicarbonate soda or backing soda then use half a bottle of white vinegar, leave for as long as possible before flushing.
Bicarbinate Soda and white Vinegar are amazing for so many cleaning jobs, I use them for all sorts..
Unblocking drains - half a cup of soda down the drain, half a bottle of vinegar on top, leave for half an hour then boiling water.
Cleaning the washing machine - fill the reservoir with white vinegar and put on a clean or 90 degree wash.
Anything with mould, white vinegar is amazing. When I moved into my house I used hot water and white vinegar for everything. It left a vinegar smell but that disappears.
Cleaning smelly fridges, bicarbonate of soda will soak up the smell and white vinegar will too. Lemon’s are also good.
Carpet stains, again soda first with vinegar on top. Rub it in let it dry and hoover up.
Other tips, tooth brushes get into little corners.
I only use spray or floor wipes on my bathroom floors, they are too small for mops and to many corners a mop won’t get into. I get on my hands and knees so I get everywhere.
I use toilet roll and kitchen paper, I hate having dirty sponges and clothes after cleaning a bathroom. Toilet paper I obviously flush, kitchen paper straight in the bin.
Another fantastic all round cleaning product is cream cleaner, like a Cif, but most supermarket home brands are just as good and cheaper. I use it for cleaning my windows, oven, shower screen, hob, it’s amazing at lifting baked on dirt. Apply it, leave it then clean it off with a damp cloth.
As you get use to cleaning and feel confident you will find other products out there that don’t cost as much as dettol and harpic.
wear gloves and old clothes if your worried about germs, you can strip and wash them straight away. I’ve been known to don a face mask when cleaning too, I have a compromised immune system and feel it can get to the back of my throat and chest, especially with lots of chemicals. It’s why I like using more natural products like vinegar and soda.
Good luck