hello! just checking out this deck, and for it to be an affinity deck there isnt that much affinity! we gotta have the ability to play whatever, whenever we like haha.
Thoughtcast will keep your budget and give you card draw. UB Affinity looks strong, but im sure Esper Affinity would probably be strongest with current card use in modern. Im on MTG Gatherer right now and im seeing tons of fun looking cards that all have affinity. and for those reading who might be thinking about making it a bit faster, but for a few more buck of course,
Mycosynth Golem looks SUPER fun haha. overall, nice budget build!