First of all I can say you dont going totally wrong on this approach. Making a $50 combo deck can get a bit tricky. We in our Playgroup build 50€ Decks (we are in Germany) for each other. So not building for ourselves :)
But before i mention any cards, what are your thougts about the deck? Do you want it to be a fast combo deck - trying to assemble combo as fast as possible and your only win condition? Or more like combo control - you stall the game as long as possible and then finish off with your combo ? All in all, to find your combo you need more card draw. Especially on small budget because the tutors are limited. Do you want that we mention cuts and adds? or you want doing on your own and just some suggestion?