Do not produce art piece because you want to sell. But produce it because you want to jealously keep it. That way, art collectors will bid high for your work.
Buy high quality materials that will stand the test of time. Durability is one of the assets of valuable art icons now in the world.
Don't live on your artworks. if you do they'll cheapen your rare God given talents and skills. Look for another means of living.
Be a good orator before your patrons, observers, commissioners, etc who visit your gallery.