Just a clarification.

I am doing this for the first time and just need to be clear. I just downloaded sims 3 and all the EPs and SPs. I am starting the installations. Do I need to do the cracks that came with each download as I go or just wait till everything is installed and use the ones from the ultimate fix?

1) Download all EPs/SPs you want.
2) Follow the Mac guide to installing them (it's on the "All Downloads" section on games4theworld.org), for me at least, the installation order didn't matter, as long as your base game is installed first.
4) Do not apply any cracks, though, you need to open the installation guide in each EP/SP to find which serial code to use. (If you having issues with "regional code" look on a older post on the forum).
5) Download the ultimate fix for mac and follow exactly what it says.
6) You might need to restart your computer and/or close some open windows. (I found my game wouldn't start up the first time around, but it worked after restarting my computer).

Hope this helps

I was able to get it updated. But I can't get it to run.

Oh. Hmm, I'm not sure about that one. I got "Files Have Been Modified" Error upon the first run when I tried to update. But I don't think it was ever able to successfully update to 1.24. Ive checked for new updates but it says by game is "up to date". I suggest removing the update then? Hopefully someone can help you out more. If not, then I hope you haven't deleted the .dmg files, so you can do a quick re-install.