Reddit mentions of US Art Supply Large Mouth Single Dipper Palette Cup

Well, flake white is one color you'd want to avoid. It's made with lead. Gamblin makes a flake white replacement that's supposed to be very good, though, with all of flake white's handling properties but without the lead.

Cadmium colors are toxic but only if you breath or ingest the pigment directly. Wash your hands after you use it, and if you have to sand down a painting with cadmium in it, take it outside and wear a good filter mask.

For a medium, linseed oil or walnut oil + a really clean odorless mineral spirit like Gamsol would be a good bet. Mix them about half and half. Instead of keeping a big jar of it open, just get a little medium cup like this one and you'll have, at most, only an ounce of it out at a time. If you don't even want that much you can try an alkyd medium like Liquin, Galkyd, or Neo-Megilp. With pretty much all my paints, I mix in a few drops of walnut oil into them when I first squeeze them from the tube, as that not only helps loosen them up but also slows the drying time a bit; because they've already got that bit of extra oil, I don't need to use a ton of medium, so I've usually only got a couple of teaspoons of the stuff out at a time, whichever one I'm using.

For cleaning your brushes, you can also just use straight linseed oil while you work; just keep a container of it handy, dip your brush in, and wipe it out on a paper towel. (I like these Scott shop cloths as they're specifically made to soak up oil well.) It's not going to get all the paint out, so you'll want to have plenty of brushes so you can swap them out between colors, but it'll keep any paint that's left in there from drying out right away. If money is an issue you can use mineral oil or baby oil for cleaning, just make sure you get it all out of the brush before you pick up a new color. I did this for awhile when I first started and didn't want to invest a ton of money; getting some of that oil into the paints probably didn't do any good for the longevity of those paintings, but they were just shitty ones I was doing to learn how to use the paint anyway so it doesn't matter.

At the end of the day you can just wash them out in warm water and a good brush cleaning soap like Pink Soap from Speedball or Studio Soap from Richeson. (When I clean mine, I take them outside and give them a quick swish in some odorless mineral spirits, shake out the excess, and then bring them back in to wash. Since the OMS gets out most of paint, I don't need a special soap to finish them, I can just use baby shampoo to finish them off. That keeps pretty much all the OMS I use outside where I don't have to breathe it, and makes the final washing go very quickly.)