As far as exercises, you need to figure out how the materials that you're using work before you do anything.
Cheaper paint like Liquidtex basic will need multiple coats because the paint is of lesser quality than say a paint like Windsor and Newton Artist grade.
The better the quality of the paint, the more you can do with it but since you're just beginning, I'd go with a lower quality. I use the Windsor and Newton because it's the best I've found and it works really well for the way I paint. It's a thick paint and it covers well even if you thin it out.
To establish your pallet, I'd say get crimson, cerulean blue, cadmium yellow medium, titanium white, ivory or mars black.
with those 5 colors, you can pretty much mix any color you want
My advice is always paint what you see not what you think you see. That comes with practice. I'd say get some canvas boards to practice on. They're cheap and hold paint pretty well but not as well as a stretched canvas. A painting on a canvas board won't last as long simply because it's canvas over paper or cellulose.
I really don't think that anyone can really teach technique. It comes with practice. What works for you won't always work for someone else. My painting instructor had us do a version of gradients as our very first assignment.
We used a yellow hue, red hue, blue hue, white and black. We did 3 shades and 3 tints of each. For the black and white, we started at a pure white at the far left hand side of the board and worked our way to pure black. The middle block was grey. The next block to the right was a darker; the next one was darker still, and the last one was pure black. The first block to the left of the middle block was lighter, the second block was lighter, and the last block was pure white. Do that with the yellow, red, and blue-you'll have pure color in the middle block and the darkest shade to the far right and the lightest to the far left.
I would however suggest taking a painting class at your local college if one is offered. You'll be with other people and you can watch them and adapt what they do to fit your needs. You'll probably have critique sessions where the instructor and other students offer their opinions.
I love painting. It frustrates the living hell out of me most of the time but I love it. I enjoy playing with colors and seeing what works and what doesn't.
Invest in good brushes-you can skimp on the paint but not on the brushes. They're your tools.
If you live someplace with a good art supply store, go there and I'm sure they can give you some good advice. If not, use dickblick.com to buy supplies. It's really a great place to buy and research materials.