Trump is not spending money on ads, because he gets so much free air time for the cable news outlets, he has no reason to.
Since it's the GOP you would expect that Fox News gives Trump the most airtime, but you would be wrong.
MSNBC and CNN are much more into the Trump mania than Fox News. In fact Fox Business has talked about Trump more than its big sister.
Here is the graph of who is pimping the Donald the most:
H/T Mother Jones