Painting to sell at high end art galleries

Hey y'all, I am an artist who has so far only worked for leisure and would like to take the giant leap to start selling and I want to create art to specifically sell at high end galleries. My 2 questions are 1. Will using oil paints help me to amp up the prices the most I possibly can? 2. Do galleries prefer paintings on canvases or a certain type of paper? I have only painted for myself and have no formal training so I am clueless about this. It's ambitious but I believe I have what it takes. Thanks and any other advice is welcome!