I have already watched and enjoyed the following:

1. Weightlifting Fairy

2. Love 020

3. Noble My Love

4. Pride

5. BuzzerBeat

6. Something About 1%

7. Bromance

8.Boss and Me

1. My Sunshine
2. Fabulous Boys
3. Shopping King Louie
4. Sassy Go Go
5. Black Demon and White Prince

oh my dear friend there is so much i want to recommend! 
if you want a light hearted drama with a good plot then there is a lot of dramas that is a must watch!
for example i would say:

lucky romance - very light hearted, so funny because it starts with the female lead trying to find a person who is born in the tiger year, she need to be with before her sister will get any better, her sister is in coma, i just ended the drama and im so in love ith it and couldnt get enough of it
she was pretty - about a girl who was so pretty when she was young but by the time she gets uglier with the years. in her youth she was very good friends with a not so cool, chubby guy that gots bullied one day the guy needed to go to the USA and never saw female lead. after years the female finds the male lead again, and wants to meet with him again, but something went wrong, and the male lead thought the female leads best friend was her, because she was pretty. the female lead gets a new job at a company where they just got a new director - her childhood friend!

drinking solo - so light hearted! VERY FUNNY! about some roles and supporting roles who are drinking alone, and then we hear their reasons to drink alone! MUST WATCH!

oh my venus - also very funny one! about a girl who also were very pretty and thin before, but because of a sickness she have, she gained a lot of weight by the time. then she finds a trainer that can help her, who is a well known person. while helping her, he falls in love with her!

i gave them all about 9, 9.5 and 10! xD
and then there is also some like:
introverted boss
pinocchio
legend of the blue sea
jelousy incarnate
cinderella and four knights
cheese in the trap

but some are not sooo light hearted as others xD
You're Beautiful
She Was Pretty
Hana yori dango
From 5 to 9
We married as a job
Soratobu kouhoushitsu
The greatest love
The master's sun
Oh my venus
It's not that I can't marry but I don't want to
Tokyo Tarareba musume
Kill me Heal me
Healer
Hotaru no Hikari
ikemen desu ne

You should try watching My Secret Romance, its currently airing. It's currently one of my faves. All the good stuffs are already mentioned above.