Dies to Removal

I've been only working on Standard but as my collection grows I was considering trying to slowly acquire some useful Modern cards to assemble a deck. It seems like Affinity is an archetype that really stays around and is not incredibly expensive. It also looks like a fun aggro deck. Is it worth it to trade my way slowly into a Modern Brobots deck, or is there another similarly expensive type of deck that has more potential? Granting that metas shift all the time, but will this tend to be a competitive deck?