Knock down as many GE courses as possible towards the IGETC completion.
Ideally, you can take in the first semester:
Calculus 1
Eng freshman
GE
GE
The following semesters, you might want to start the physics (only for UCLA and UCI) and CS (UCLA) sequences (check assist.org if you need to start the CS sequence in your first semester as you may have to take a CS intro class to get into the CS prerequisites).
Personally, I didn’t take the physics nor the CS sequences because I hate physics, but I couldn’t be a competitive transfer for UCLA and UCI as a math major.