Reduce scripts using processes/resources mediawiki

I switched over to Dreamhost for over just under a month. I have noticed my website would freeze intermittently (at least 2-3 times a day) with an eventual 500 internal server error. Support desk at DreamHost told me …

“it’s just a matter of your scripts
requiring just a bit too many resources come high traffic. You will
continue to receive these error messages unless you find a way to lower
it’s resource requirements or move to a PS.”

Thing is my website gets about 800 visitors on a busy day. I am using Mediawiki. I think PS is out of the question until I get more users, but in the meantime could someone offer tips on reducing processes usage so I wont encounter these lockups?