Water color and Acrylic painting

Mak

I am trying to get better at using water color paints and acrylics. Does anyone have some advice for a beginner? I don't paint realistic things. I usually paint very basic simple things, but I want to get better. What are some things I can do to limit how much paint I waste? What is the best, but also most affordable paper to use. How do I use water color over a sketch but hide the pencil marks?