I don't know of a single artist who became professional after his first oil painting!
Karin Wells wrote an article here which I cannot find anymore, entitled "So you want to be a professional!" It said quite plainly that if you want to become a professional, you will need to dedicate months and perhaps years of daily painting and serious study to become proficient enough to market your work seriously.
You have a very good start. Keep it up. Let me suggest that you study the palettes of the masters and even of those who have posted their palette remarks here. You will, as I have, learn a great deal.