Oh my
I totally didn't expect to win, I was sure ClayMask and LenaLJ would greatly outperform me as usual. But now I see that they haven't participated. And I completely restarted my computer system a few days ago, so I can't even check some things I don't remember
My strategy won't be full because of it. I'll just do my best and write my key moments. Also, sorry if I get any names wrong - my game's not in English.
So, I played with a male sim. He had Loves he Outdoors (to have a +2 happy moodlet all the time), Ambitious (since we needed a lot of promotions for the challenge), and the third trait I can't remember, sorry
His initial aspiration was Computer Whiz (to get a skill leveling boost). After the start, I changed it to Soulmate immediately. He met Zoe Patel and quite quickly completed the aspiration by marrying her (without moving her in, of course) and all the other stuff. During the process, he fell asleep on the ground and peed himself a few times, which counted towards my multiplier (it didn't really bother him because of a ton of positive moodlets from interacting with Zoe). Zoe is a great "guest wife" because she's unemployed and can come whenever called, never saying she's busy. Since that day, he always invited Zoe to come, usually twice a day. Completing the Soulmate aspiration gives two amazing boosts - renewing their wedding promises near the wedding arch (which gives +3 to Happy for 2 days) and also an instant big boost to all needs (don't know the English name, it's something like "sharing tough times together" by sense). That was making my sim pretty much always in a great mood. During the whole challenge, I didn't really try to get a lot of Misfortunes, because for me it was easier to concentrate on skills, asps and promos. My sim never had a bed on his lot, and the toilet bowl was moving back and forth from the inventory to the lot (sometimes I wanted him to pee himself, sometimes not because he needed to do something useful urgently).
The next aspiration was Computer Whiz. In the very beginning of the game, he joined the Tech Guru career, so he was level 2 already when I chose the asp. This aspiration, again, has two huge advantages. First is that, upon completion, you can get job meter boosts. Second is Research binge which raises all of your skills at once! (except the ones that came with the addons). So basically, all the rest of the strategy was completing this aspiration, then getting level 2 in each skill (Research binge doesn't work until the skill is lvl 2), then using Research binge until all my skills were lvl 6 (it can't go higher with Research binge). Voila, lots of points for the challenge
I quickly raised Charisma to lvl 10 to get an opportunity to ask for a bonus, which also helped the job meter. Now I could easily get a promotion on earlier levels in one day. Then, basically I worked on all aspriations one by one, raising skills further where needed and getting career promotions where needed as well. I can't remember all the careers my sim worked in, but the first one was definitely Tech guru to lvl 5, then Culinary to lvl 8 (I guess, can't be sure), and also a few levels of Entertainer, Painter and Sports.