The best way to start imo is to buy at least the basic morph sets created for your figure of choice, then load up that figure and just start playing with the morph dial options until you get a solid feel for what each of them does with the head and body mesh.
Don't be afraid to use negative values, even if you sometimes have to turn off limits.
I prefer to do the dial spinning on the character with no texture applied, just a flat mono-colored "clay" look. It makes it easier to see the effects.
Find photo references of faces, facial features, and body types you like and practice recreating them as best you can with the morphs dials you have. Real life has a lot of variety and is a good inspiration even for fantasy characters.
I usually start with a facial feature I particularly like and then create a new face from that, rather than trying to completely recreate a face from a reference.
Rotate the character around to see what the face looks like from various angles and adjust as needed. (Sometimes using a dial that changes the shape of the entire face will give me a result I don't want and I have to fix it. For example, I used a small amount of a creature head morph on Dawn, which made her ears longer and pointier. I didn't want that, so I had to adjust the ears to look more human again.)
For your own use, you can mix commercial morphs, commercial characters, and free morphs. If you're going to do any commercial products, though, you'll need to stick with the commercial morphs that allow you to make characters for redistribution.
Save your finished dial-spun character as a character preset.
You can also make a character dial -- which will then let you mix the features with any other dial-spun characters you create -- by following this tutorial:
Create Single Dial Morph Control In Daz Studio 4.9 - Digi-Dotz 3D
Hope that helps!