A running rig is basically a lead that isn't fixed on the line, it can slide freely. Go in to your local tackle shop and ask them to help you out and show you what the running rig consists of. I personaly don't think a running rig would make much difference to you catching. Try concentrating on smaller bait sizes, and maybe you could try putting out a lot of bait out instead of just pva bags.
good luck mate
:)