You need to define what is "good" and "normal" FPS. What's good or normal to you might be wonderful or terrible to someone else.
You need to provide as much information as possible about your system, what's running when you're gaming, specifically what all games are you having trouble with, have you downloaded the latest patches for those games, what drivers you updated, are there any games that run just fine on your system, what version of Windows are you using?
I also second the advice of switching to Avast from AVG. I would also suggest not running without a firewall. Try Comodo Firewall, Zone Alarm, or PC Tools Firewall Plus. They all have free versions available. If you have the money for it, there are really excellent suites available that cover anti-virus, firewall, and other features not included in free versions. Personally, I use Kaspersky and have for years. Bitdefender is also good. So is the pay version of Avast.
Also, try something like GameBooster
. It's free until June 30 from their website. It shuts down all of those unnecessary Windows processes while you're gaming and restarts them when you're finished.