do you have diploma already? which course/school was it from?
imo, it is not very useful lar. i think you'll be better off doing a advanced dip which would teach you some graphic design or web design skills. such skills are quite useful for marketing professionals.
alternatively, you can also do an internship or get a temp/part-time job in this field, if you want to give this field a try. nothing beats real experience.
certification doesn't carry much weight for marketing jobs. you'll be earning the same as diploma grads lor.
I just finished this course last week, not sure about the salary but definitely its a value added to your career path in case you want to change jobline or even strike on your own
Tough course if you ask me. But good substance. Good luck!