First of all, congrats for your 3rd place ! I would be happy to loose my discipline and do that... Instead I'm going broke generally
Regarding your question, I suppose you should not jump from $5 to $40. But you should not stay at $5 forever neither. Therefore try some $10 or $15, play a little, just to check the differences between your current level and the upper. The game come tighter and tighter. And just come back from the level you are having some issue with, to the level where it was OK, to optimize your ROI and learn. And go back on the next level when you're good again, etc... etc.. Up to the million.
Good luck !