i think that 3-4 are plenty especially from really good sources that can help you..you do not want to over do it so choose your best ones and if i am right some universities might have a limit..do your best!

You should only supply as many as the school asks for and no more. Most schools will want one from your counselor, a math teacher and and English teacher. If they only ask for two don’t give more than two. Oddly enough, some schools don’t want you to send any at all. Read the application requirements carefully and twice or three times. If there is no mention of how many letters of recommendation then you can send a few, not too many or they will not read them all. Five (give or take a couple) is good. I think ten is too many. Make sure they are from someone that the school will find reputable like your teacher, principal, pastor or priest, coach or boss. Someone who knows you well and is in a position of authority. Don’t send in something from your parents or an Aunt/Uncle or neighbor.

Many colleges will tell you how many and who they should be from. Assume nothing, check with the schools.

In general, three is an often used number for letters.

The people who write them needs to be “across the spectrum.” School; Personal outside of school; Personal who is involved with you – organization, church, job, etc.

I think that has a limit. Depends on the school.