I recommend:
1.)
All About My Romance- It's a light drama with a great pairing. There is no real love triangle (love square in this case), although both leads have to deal with second leads with a crush. The male lead chases the female lead, so there are a lot of great scenes of them together.
2.)
Secret Garden- It's a very popular fantasy drama. The two leads have some of the best chemistry I've seen in a drama. There is no love triangle (although the male lead does get jealous from time to time). As in the first drama I recommended, the male lead chases the girl, making for a lot of great scenes. Although I wouldn't classify it as a light drama, but I wouldn't say it's heavy either.
3.)
Panda and Hedgehog- This is a very light drama. In fact, there isn't much of a plot. There is a love triangle, but it's handled with impressive maturity by both the female lead and the second lead. I liked it mainly because of the characters. I liked the back story for the main characters and the relationships built within the bakery.