Question about PHP-CGI, mysqld and sudden spiking average load readings on Linux Virtual Dedicated Server running CentOS 6.3

I have noticed when doing a "top" via SSH on my GoDaddy virtual dedicated server that every time a user logs in in the COMMAND column I see the PHP-CGI process start to run, followed by mysqld. Often when these two processes run I start to see a spike in average load, and sometimes this spike spins out of control to the point that when trying to log on to my Moodle 2.3.2 LMS I get an 500 Internal Server Error from Apache. Now, what I'd like to know given the fact that I have only 2GBytes of RAM and am sharing a processor with other users :-( is if there is any way to make sure my PHP 5.3.3 is properly configured. I am given, for example, a choice between CGI, fastCGI and Apache in my Plesk panel, and I am not quite sure how to optimize things for my environment. I went to the Moodle.org site to try and see what's the right setting, but it's not clear if the persons writing there have a different setup or not. Unfortunately, it's impossible to get specs on my VDS's processor from the fine folks at GoDaddy, and perhaps there is just a simple processor power issue going on here, but I only have 30 students and only a handful going in simultaneously. And at times my average load can move from .08 to 1.5+ and all the way up to 2+ within the space of a few seconds. I should point out that at one point it was discovered by GoDaddy technicial people that a user was running a rogue process that overtaxing resources. But perhaps I also need to tweak my installation despite this incident. Any help here would be appreciated.