I normally get the spouse and/or helpers first and set them up in their efforts to get the dynasty started (I check the status of their painting skill, get gardening/fishing/sculpting/painting underway, have one/more of them decide they really didn't want to be a <insert rabbit hole career> as their career at all, and of course sell stuff they brought with them to get a somewhat decent house started with things to help them do those things), as they are doing that, I usually set the founder up with planned supermaxed skill and career (usually self employed career). I leave other requirements especially best friends until later on. As Ratchie has said earlier in this thread/elsewhere getting that portrait of the founder completed before they become an Adult is mandatory. I let the other requirements play second fiddle to that initially. As an experiment, I tried a sim with the artistic trait but no painting skill (Emma Hatch) be the painter. She achieved the necessary level of painting for portraits and the founder still had a week to go before aging to Adult. I haven't yet tried that with a non-artistic sim.
In that same game, my founder is pursuing the double whammy of guitar supermaxed skill and one sim band life time wish. In this case, I spent the first week of the game on him simply playing the guitar and raising that skill. Once his guitar got to about level 8, I got him employed at the theatre. He kind of flew through the levels of the career, as I was hoping he would. He is now level 8 of the music career (Rock Star branch) and 8 of 10 guitar opportunities away from supermaxing guitar (other skill challenges in guitar are done). He is 3 days away from elderhood. So once the guitar star challenge is done, he will be taking classes in drums/piano/double bass and working on finalising his life time wish. (I have useful elixirs and a motive mobile on hand to make this as painless as possible).
Personally, I leave best friends to last, and bringing in the next generation (especially when playing a male founder) as late as possible, though that depends on your spouse as well (eg if your female spouse is close to elderhood, you'd need to bring in the next generation sooner). As all five of the roomies household in Sunset Valley have moved in to assist in my current game, I did the heir a bit earlier than normal, as there were others around (three self employed sims) who could help with the toddler skills. I wait until the money starts coming in and then buy the property and building, and upgrade the property as well, so I don't forget to do so.
