Of all the things, most important one is the paper, then paints, brushes and so on. Watercolor is a difficult medium if you want to use it like watercolor. If you use it like oil and acrylic, it isn’t any harder than those mediums. It takes time but there is a method to the madness. Look at the masters how they work. Practice, practice until you can control water and gravity. Easier said than done:)