How many schools you apply to is based on several factors - here are two big ones that come to mind:
1) How strong is your application as a whole (GPA, OAT, extracurriculars, personal statement, etc)? A weaker applicant obviously should apply to more schools e.g. 5-7 schools.
2) Where do you want to go to school? This sounds so mundane but it's very true. I highly recommend not going to just any school just because you want to start school right away. The school you choose is pretty important, so even if you don't get accepted in the schools you want in the first time applying, it's okay to re-apply again next year, given that your OAT is still valid, etc. What's the reason to rush anyway?
IMHO of course - others will likely have different opinions.