Hello!! I want yo watch a rom com drama with ghosts. Also I don't  want anything too heavy or melo. Which one do you recommend? Oh my ghost or Bring it on, ghost?

I absolutely adored Oh My Ghost! (*^_^*)
Watch Oh My Ghostess & afterwards watch Bring it on Ghost because BIOG has a more lighter plot line than OHG, and so it'll make you feel better about whatever you feel after watching OMG~ :) 
Oh my Ghostess and Master's Sun

Arang and the Magistrate?
If you don't mind movies you should also check out Spellbound ^.^
Bring It On Ghost was really good
This is my top 3 of ghosts dramas:

1. Oh my Ghostess
2. The master's sun
3. Bring it on ghost!
if u like rom  com drama just go watch master's sun you will definitely like this drama
Top 3

Master's Sun, Oh My Ghostess, and Chicago Typewriter (although CT wouldn't be strictly rom-com...so that one might not top your list, but it was amazing nonetheless.)