That looks like a nice piece of kit especially as it will weld gas or gasless.
Mig is certainly the one that most people start with as teaching yourself using the welding forums as guidance is very achievable.
I bought the Clarke 135te as it came with everything I needed inc. gas, wire, tips, nozzle etc.
The review on the one you're looking at says it has 135 amps. If you use the calculator on the migwelding forum it tells you that the max you'll be able to weld with full penetration is 3.5mm. MarksDTM told me it's nearer 2.5mm and having done loads of oractise I'm inclined to agree
. However, if the work you're doing isn't critical (I.e. If you get it wrong you're going to die) then 4 mm is probably achievable.
I'm not the sharpest of cookies but I've got comfortable with mig now after a few hours of practise. Some guys say you should be laying beautiful welds in half hour lol 'dangle berries'
As long as you have lots of time to learn you'll be good