While a cheap AC set from machine mart is OK for small jobs, and learning the basics, you havent welded until you have used a high frequency inverter set.
the difference is night and day! and they are very small and compact.
the real advantage is that being high frequency your arc doesnt have 2 chances every second (50hz) to blow the arc out and stick the rod to the workpiece. its a bit more like DC but without the other issues like arc blow etc.
My mate has an inverter set sealey one and thinks its the poodles privates!
and i think i agree, i managed to weld a patch on a car with it using a 1.6 rod with no slag traps or holes burnt, just like using a mig!
its the ability to sustain the arc at low current that makes the difference.