「カッコイイのやってみたいと思ってます」 What's meaning of の here? How I understand: (I think) I wanna try to do something cool? (I'm not sure about カッコイイの) Thanks for your answer
「カッコイイの + を + やってみたいと思ってます。」
「の」 is a nominalizer that turns the adjective 「カッコイイ」 into a noun-like form - "a カッコイイ one".
What the thing is should be clear to you from the context. We have no way of knowing it here.
"I'm hoping to pull off a good one."
(I just used the adjective "good" because I do not know what the object is that is being talked about.)