Using a sandbox while browsing is a good idea. There is a free one called sandboxie and it will be good to try it. I use it everyday but the paid versions of avast have a sandbox so if you have a paid AV you don't need sandboxie. ;)

Avast sandbox is not the same as Sandboxie. Avast sandbox does not protect your browser from unwanted changes. It analyzes unknown programs to see if they are safe or not when executed. Sandboxie is a browser protection first and foremost. It does not have any sort of detection means. Using a system image is always the best route. Every security product will fail at some time or another. Thats why its best to have a backup solution. Unfortunately most users fail to back there pc’s up.