>>3542854Watercolor is pretty basic but still gives you lots of options in regards to technique. And can probably do more stuff that digital painting can't than other paints.
If you want an opaque paint, choose tempera.
Don't start with oil because there's too much shit to care about besides painting itself. Oils need solvent, canvas, lots of care of your brushes, fresh air so solvent fumes won't make you sick, time to dry.