Artists should always use the best materials available and their budget will allow. Not only does it make a significant difference in the final aesthetic outcome and archival longevity, but the actual process becomes a pleasure. Painting is difficult enough as to not detract oneself with poor materials and tools. Patrons and collectors expect to purchase a work that will last. This a list I am currently using, but it is ever-changing.
The following are vendors of quality art related materials.