Recently I tried Emacs and found Evil helpful to keep my vim custom. I\'m used to typing \"jj\" to return normal mode from insert mode like many Vimers do but don\'t know how to
I don't know whether it works with Evil, but for Emacs in general the KeyChord library is designed for this sort of thing.
Try it and see?
(key-chord-define evil-insert-state-map "jj" 'evil-normal-state)