I have several ideas that may work well for Bolin's love life.
My first idea is Bolin likes a metalbender. Like Bolin she is strong, fun, and GORGEOUS! They first meet at the Police Headquarters where Team Avatar was talking to Lin Beifong. In order to try to impress the girl Bolin learns how to metalbend at the Beifong Metalbending Acadamy. The girl, at first, only sees Bolin as a friend but soon starts liking Bolin after getting to know him better. Also she is Saikhan’s daughter, and he is an overprotective dad who doesn’t like Bolin much.
A Kyoshi Warrior
My second idea is Bolin likes a Kyoshi Warrior. It’s like the LOK version of Sukka. While Team Avatar arrives at Kyoshi Island where almost all Kyoshi Warriors obsess over Bolin, except one, which happens to be the Kyoshi Warrior Bolin likes. She feels he is just some stuck up earthbender and Bolin tries to prove that he is diffferent than that. When Kyoshi Island is attacked and the rest of Team Avatar and most of the villagers are captured, Bolin and the Kyoshi Warrior save the island. The Kyoshi Warrior likes Bolin in return.
Bosami as everyone calls it. Bolin feels like a third wheel between Mako and Korra and Asami is stressed out about Future Industries. In order to help their friends Mako and Korra try to find dates for them. After several failed attempts Mako and Korra realize that Bolin and Asami together were better than any of their other couple ideas. Bolin and Asami have a blind date set up by Mako and Korra. They have a lot of fun and start to realize their feelings for each other. When Asami is captured saves her after Mako and Korra fail. They confess their feelings for each other and start their relationship.
Everyone's saying that Bolin is going to be with a spirit, kind of like the LOK version of Yukka, so I might as well explain why and how it won't work out. Bolin and the spirit first meet while Team Avatar was in the Spirit World fighting the Dark Spirit. The spirit helps Bolin escape the Spirit World and they fall in love. After that the spirit visits Bolin in his dreams. Korra finds out and tries to stop the spirit from seeing Bolin, fearing it's a trap from the Dark Spirit. The spirit thinks Korra is jealous of her and Bolin's "relationship", if you can call it a relationship, and joins the Dark Spirit to get rid of Korra. The spirit seems to have gone crazy which leaves Bolin no choice but to dump her. The spirit says she will return for him, leaving Bolin scared for his life. So yeah the story might suck but so is the idea of dating a spirit. No offense Yue.
Comment other ideas you have for Bolin.