i think bronze is fine as suggested, maybe go even lower than 10% and put it all into silver instead. to me bronze leage is more like a tutorial stage where you arent actually supposed to earn anything. you test out the game and see if you like it or not. if so, you buy into silver. i cant imagine any player being in bronze actually enjoys it longterm since most cards have hardly any abilities and gameplay is rather dull. getting the masses into silver should be the goal imo.