When I'm working on a new illustration, the first thing I do is draw a rough sketch of the figures and the layout. For this drawing I used a photograph of mine as a reference. It helps me get the right perspective. My favorite pencil is a 6B because it flows so smoothly on the paper. My favorite paper is Strathmore Hot Press watercolor paper. I like that it has a smooth finish, which makes it easier to scan into Photoshop without added texture.
The next step is adding details. I figure out character expressions, clothing patterns, and environmental details. I use my super skinny Tombow eraser to remove some sketchy lines and start establishing a cleaner look.
Then I add watercolor. For professional use I like Schmincke and Winsor & Newton. I obsessed for months about what brand I liked, and then finally realized it didn't matter. It's all about how you use color to tell your story. If you pay attention on Instagram, you'll see a lot of top artists use very inexpensive watercolor sets. But that doesn't diminish the quality of their work.
Finally I scan my drawings into Photoshop and clean up unnecessary smudges with Levels. I scan my favorite drawings at 300dpi in case I want to create prints of them down the line.
Let me know if you have any other questions about my process and favorite materials.