Uppers + Skeelz 1/2 deck (5 Uppers + 3 Skeelz) is a wonder combination!
Skeelz is the better mono deck simply because Uppers have some of the weakest selection of 2* characters. But you are best off combining Upper's dominant big characters with Skeelz's useful small characters.
If you want to be super aggressive: Dorian, Nellie, Kayazan, Rubie, Oxen, Redra, Liam, Sasha. Of course there are a lot of other takes on this as well.