I like your version. You chose some powerful cards.
I would like to contribute to your deck with the following reasoning: The best discard is the cheapest discard. Since you are running 20 lands, you are expected to hit 4 lands after turn 4. This means that your Madness creatures will have less chance to make an impact early in the game if you don't open the free discard spells like
Wild Mongrel. For example, if you have 3 lands by turn 3 you can curve perfectly
Wild Mongrel and
Arrogant Wurm. By the other hand, if your discard outlet is Baazar Trademage, you won't profit from Madness until you hit 6 lands (which is a lot, by the 20 lands deck standards). I would include
Fauna Shaman in my deck if not by budget restrictions and I like very much
Merfolk Looter.
tl;dr: The more mana intensive your discard outlet is, more lands your mana base will need. Or, the cheapest discard outlets free space in your deck to fill with threats.