for legacy versions i would suggest combing channel9 or grabbing a plural site acct.
alot of the legacy certs have been deprecated and would only certify you as a farm admin or dev (not the inbetween of content/site collection admin).
If you are going the site admin route, this is pretty much the owners manual IMO:
https://www.amazon.com/Microsoft-SharePoint-2013-Plain-Simple/dp/0735667004
What version? This is pretty much the defacto user manual IMO:
https://www.amazon.com/Microsoft-SharePoint-2013-Plain-Simple/dp/0735667004