Which candidate spent the most money in Iowa? Jeb Bush, who ended up with 2.8% of the vote. His SuperPac spent millions on ads attacking Marco Rubio, who eventually got eight times as many votes as Bush did. The goal of all that spending was to keep Rubio from earning a strong third-place finish that would allow him to portray himself as the leading establishment candidate, which is exactly what happened.
I would not be such a fool as to argue that money means nothing in politics, but right now it doesn't seem to be helping Bush or Clinton very much. Despite what one sometimes hears from frustrated progressives, it's hard to buy an election in America.