Use mods. The whim system actually makes sense with mods. The original whims are just...buy furniture from packs you own. Modded whims are so great. And if you're feeling spicy, add the mod Better Sims from MTS by Midiar. It adds some features that I think really give the sim personality. It adds in these features:
Complementary Traits
Talents
Color Preferences
Style preferences
Randomized Fashion choices
Location Preferences
Hobbies and skills preferences
You can either add them yourself to customize them, randomize them, or let them be found while playing. As in...if you cook for the first time, if the sim likes it, they will say something like I really like this activity and enjoy doing it from now on. If they don't like it, they will say they don't like it and then get a buff saying something like why do I have to do things I hate. It's pretty awesome and I really find that having my sims like and dislike things adds a lot of flavor and I can put them in clubs with other sims like them or I find out that they just don't get along with certain people.