Chain, cassette and chainrings get pretty ugly at times, but that depends on what you use for chain lube. I have used lots of chain lubes over the years. If you ask 100 cyclists what to use for chain lube, you will get about 150 answers. Yes, I know I did not tell you what I currently use, just explaining why, I probably will change my mind in a few months.
Cleaning chain, I put a bit of kerosene on a paper towel and turn the crank while holding the towel against the chain. Same for cleaning chainrings. Cassette, I usually just use some cheap gardening twine like floss to clean between the sprockets and don't bother trying to get it cleaner than that. I have some disposable gloves I got from my dentist office, use those when I use kerosene but I do not dispose of the gloves until I get a hole.
Cleaning other surfaces, mostly just soap and water. High pressure water stream can push water into bearings, I never use high pressure water except on tire tread and sidewalls. Otherwise mostly a water mist with soft brush. Dawn dish soap is a good grease cutter. I have some auto cleaner/wax that I often mix up a bit with a couple gallons of water and use a soft brush for frame, fenders, etc.
I have bought some brushes at the dollar store that I only use on greasy parts of a bike, for example chainrings, I do not bother trying to clean those brushes. Sometimes I put a dab of Dawn soap right on the brush if I start cleaning something that is really ugly with greasy dirt.
For grease, usually use Phil waterproof grease, but sometimes I use some Pedros, I have both. But if you want a suggestion on which to buy, buy the Phil.
I use blue (removable) threadlocker on rack bolts, shoe cleat bolts, fender bolts and kickstand bolts. All other fittings like water bottle cage bolts, stem bolts, etc., just use grease. Last time I needed some thread locker, this is what the hardware store had, but I have bought several similar products over the years:
https://www.truevalue.com/6-ml-remov...hread-locker-1
From the photos, I can't tell if your bike is black or a different color. I bought some black fingernail polish at Dollar Tree, use that for touching up my black racks and other black parts. Frames, I usually look for a fingernail polish that looks close for color. If you have bare steel and want to cover it to prevent rust but do not have any touch up paint, some clear fingernail polish would protect the metal until you can put the right color on it.
Back to tools for a moment. There are dozens of chain checkers out there. If you get one, read this first.
https://www.velonews.com/gear/measur...ar-accurately/
I bought the Pedros one that Zinn cited. Park makes a similar one if you want to stick with Park. The video is good for both teh Pedros and the Park.
I replace derailleur chains at 0.75 percent elongation, chains on my internally geared hub bike I replace at 1.0 percent.