If one single person blocked you, you should be able to add anyone else you know as a friend. Being blocked by one person only affects your ability to contact THAT person- no one else.
Someone blocking you from their account will have nothing to do with you adding other friends. When someone blocks you, you can not longer see their page, send them messages, etc..
If you can't add any friends then either nobody likes you or there is some other issue with your Facebook account.
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