Review on AdSupply by Mike Rubenstein

They allow you to create different sizes of ads, so that it can fit almost any size screen (mobile or desktop).

It's very easy for beginners as well! I also love how they have many options when choosing placements in an auction - from CPC only bidding until Bidding is open all day long; there are lots of choices depending upon your needs/budget etc., but nothing specific stands out yet :) Great platform which allows me manage multiple campaigns across various networks at once without having too much clutter everywhere!!