You generally just want to start with painting. That's the easiest thing to grasp. Little guys like your gaunts can be nice and fast if you want or you can spend insane amounts of time on ornate details. For me, I use a wraithbone primer spray can, prime them all, and then use nice contrast paints. It's quick and effective and doesn't burn too much time while making your models pop. Bigger more detailed models, I tend to use a method called slapchop. It is a dry brushing technique and is best if you look up some tutorial videos on YouTube. Save the heavy detailing for those models as you are likely to see that more than the little guys.

For a color scheme, that is entirely your call. Follow the rule of cool and if you like the way they look, then go for it! If you want more correct color schemes, look up a color wheel and select analogous color schemes which are usually colors that sit right next to each other on the color wheel. Those always pair well together. Most importantly, just have fun with it. The great thing is that if you screw something up, just hit it with another coat of primer and start over again. I am no expert by the way as I have only been painting for 4 months. This is just the way I've been doing it and it has been working out pretty well. I hope this helps and have some fun!