Cheap scope + not setting parallax correctly = what kind of groups?

[Guest t.bird]

I posted about my longer-range accuracy issues several months ago and decided after that thread that I would try a few different bullet weights to see how much it would affect my groupings.  I finally made it to the range this past week and discovered that ammo didn't make that large of a difference on my accuracy...I still had groups that were all over the place.

 

I'm still fairly new at precision shooting, but feel I should be getting more consistent groups.  My best group (of 3 bullets) was .5 MOA at 100 yards, but pretty much all of the other groups were 2-3 MOA and had no consistency about where they landed...and I worked my ass off trying to ensure I was being consistent for this test.  I can tell as soon as I pull the trigger when I've had a "flyer", but ultimately I just get rounds landing everywhere that I had originally felt pretty good about, which leads to my question:

 

I have realized that I am not setting parallax correctly on my scope.  I had not realized that it can have an affect on accuracy, I though it was just more of a "focus" adjustment.  I have just been setting the scope to the 100 yard marking and leaving it...it being a cheaper scope, is probably not correct at all.  What kind of groups would I be seeing with parallax not being set correctly...I'm hoping inconsistency?