As mentionend previously it is difficult to appraise works of art by an unknown aspiring artist. Here is another piece of advice. Learn something about Zen Art or the Informel, start from there and develop your own style. If block chain verification is yet too complicated for you, buy some no longer valid banknotes for a few cents, tear them in half and glue one half on the back of the painting. Keep the other half to yourself ( and store safely) und publish the number together with the painting. Thus the buyer can be sure he owns the original painting. Good luck with your endeavour.