I'd say that's entirely up to you. Applying to that many schools is going to take a lot of money and effort so make sure you do it well. If you're going to half-heartedly do any of your secondaries, I would suggest not even applying. Completing secondaries while trying to juggle a full-time job takes its toll very very quickly.
Just a quick calc of application costs:
AMCAS for 24 schools $976
Secondaries (assuming 100 per) 2400
So you're onto $3k+ without even interviewing.