I, personally, think "c u next tuesday" is a nice start. Although, if I had to choose a Ke$ha slow jam, I'd choose "Dancing with Tears in My Eyes" from her first album Animal.
If heartfelt ballads just aren't your thing, and you're in search of some party songs, I'd recommend these three tracks. The first is the album's first single "We R Who We R," which has that "Tik Tok" energy, complete with playful lyrics that tell the ladies to look "sick and sexified" and to "hit on dudes...HARD." The second is "Cannibal," which both makes me laugh and reminds me of Shakira's "She Wolf." You and your friends will have fun growling at the club, especially at the end when she says "I love you / I warned you / RAAAA!!" Ha ha ha. Just remember to keep your claws retracted.
Last, but not least, is "Crazy Beautiful Life," which is her surprisingly earnest and tolerable, albeit obligatory, made-it song that every newbie writes to describe their new Hollywood life. What's Ke$ha's like? Why, there are "parties, disasters, and friends gettin' pretty and plastered." Sounds like all fun and games initially, but then she gets real, singing in the chorus:
"Every single night we fight / to get a little high on life / to get a little somethin' right / somethin' real / at least we try / time after time / try dodging all the douchebag guys / try trading all the wasted times / for somethin' real / in this crazy life"Then she proceeds to express her concerns about people thinking she's a poser and that she doesn't deserve respect yet because she's new to the scene. But she's not apologizing for who she is and takes pride in being outspoken. So it goes from being an "I made it" song to a "I'm not going anywhere" song. It's the most subtle song she's sung yet.