I don't know the difference between the paid AVG AV and the free one I have now, but I know the Anti-Malware has the anti-spyware as well.
I'm thinking if the AVG Anti-Malware offers enough protection.
I have heard good things about it. You can download it free and the resident (all the time) scanner works for a couple weeks.Then you can run it manually to scan your computer. I use Boclean myself.
Remember, no one or two programs can possibly protect you from everything.
Your computer settings are very important.
Don't be afraid to get your feet wet, try a recommended program and see how it works for you.