diffusing my hair🌀

My hair is very, very frizzy! It's thickish and sometimes has a little wave to it, some days it's just straight, when I don't brush it it’s actually pretty curly. My hair is also super long. So I want to achieve frizz free spiral-ish curls, and lots of volume, especially at the roots of my hair. I'm not sure is this is even possible with my type of hair. Are there any products I could use, or a technique?