Puttering from my 2002 Ford Focus

I'm pretty much at my wits end. :runaround::confused::crying::banghead:
And I don't have the money to take it to a shop.
When I try to accelerate there is a REALLY bad hesitation/puttering that causes the car to jerk. It happens at all times at different speeds. I was told that it could be my O2 Sensor or/both Cadalitic Converter.

I've changed the ...
-Fuel Filter
-Spark Plugs and Wires
(when I did this, the puttering got MUCH worse, so I'm going to change
back to the old ones for now)
-Air Filter
-about to change the PCV valve

ANY HELP OR INPUT WOULD BE GREATLY APPRECIATED.

You mentioned you had replaced the plugs and wires. It sounds like you got two plug wires on the wrong cylinders. The cylinders are from the left facing the engine. 1-4. The plug wire for the no. cylinder is on the bottom right of the coil block. The 2 3 and 4 are counter clockwise from the no. 1 position.