Y'all should stop suggesting Attack Booster. It's like telling someone to play Aggro Druid in Hearthstone right now. It's so brainless to use, since that Uppercut can just be spammed and guaranteed to land the hit eventually. :v Perhaps, instead, you should invest in something that takes a bit more skill to use effectively, or is just really fun... like Crazy Vulcan or Iron Fist.
25-30k carats + someone to teach you the basics and you can hold your own against most of the people who play right now. Also Iron Fist, Stone Golem, Infiltrator, that one SF exo with the chargeable projectice (can't think of the name rn), and Exorcist/St. Valentine. (Also not sure if these exos are within price range, haven't checked RC stuff in a while)