Her style is very soft pop, and her style hasen't changed a lot since she started. Depending on what you like different songs may appeal to you, I've moslty listened to her singles though so I'll try to recommend something off them:
Her best release this year would be "yume no chikara", the b-side is also quite cool, called "get fight"
FOr last year, her biggest hit was "ai no tame ni", sales-wise, but kaze is just too cute. It has some ethinc elements. Yume no chikara and ai no tame ni would be typical songs for her. FOr older stuff I'll recommende "Hello" (in which she doesen't sing in tune all the time but.. the song is beautifuL), kizuna and Pureness.
I don't know her remixes very well, and since it's not avex (She's on Pony Canyon) I don't know if the remix CD will be worth getting. Re. was a good album, so if you're planning to get an album it'd be a good start.