You can buy decent acrylic paints at your local wal * mart or equivalent, in the craft section or at a craft store. Delta Ceramcoat and similar brands work quite well, and cost a few dollars for 4 oz or more.
The Games Workshop / Citadel painting is problematic because, for the same cost, you get half an ounce, and they have added latex (which makes it a common allergen), and it does not survive almost unused, for the latex will be deposited in the Bottle much easier.
Decent brushes can be purchased at low cost from the same sources, often in 3-5 packs of different sizes.
Plastic pallets with 6 cups cost less than a dollar in my local W * M.
At $ 4 per bottle, you'll want at least one shade of meat, a shade of metal and a brown and green. Therefore, $ 30 was probably invested in the initial investment in materials, but they are enough to last for a while. (For the color of the citadel, you are looking for the same prices, maybe more, and 1/8 of the painting).
Spray primer is useful. Any fine primer works; Krylon has a decent one in a can of about $ 5. If you don't apply a spray primer, print with white, gray or black paint.
The palette is essential, in my opinion: you put one or two drops in the palette cups and close the bottle. Less waste, and you can dilute or mix safely.
Minis to paint is the next obstacle; Michtoy.com sells excellent plastic minis in boxes; The zvezda 1 / 72d scale (approximately 20 mm) costs $ 12-15 per box, with more than 15 minis in the box. Since the techniques are the same, whether the minis are made of plastic or metal, it is an economic starting point.
Also, find a good instructional site and work on it once you have the materials.