Couple of things, do not be afraid of turning up the heat, most welders will not have enough heat to worry about over doing it, I have had a multiple, welders and have worked in many shops, I think the Lincoln will be the best by, I am a miller fan for a couple or reasons, but only 3 Miller Matics i would use the rest are not up to the task, the Lincoln
Starting off with a POS helmet will just make crap welds, the big deal about a cheap helmet is the auto dim is slow and will get arc flash, and you will be welding blind,
Get a good Miller, they are good and not very expensive,
Cheap Helmet = Cheap results,
Starting off a 140 Lincoln is a good start and portable,
Next would be a ESAB Fabricator
Even better is a ProPulse 220 - If you start to learn Pro-Pulse, you will weld like the best out there,
Millermatic 252, great machine also same in class is 260
And top of the Line will be the Millermatic 255 I personally own a 255 and it does ProPulse and can change the inductance,
the only 2 machines right now that you can change the Inductance is a HTP, Miller and Esab, to have the perfect weld, it helps with adjusting the Inductance, especially the Miller 251 has a low Inductance and will never produce a great weld,
After having 3 Millermatic 251 it has auto runout timer issues and inductance issues, so i would stay away from that machine, 250 has the same issue, was fixed in the 252 Models,
Lincoln is a Great Machine but feel is overprices in the 240V models compared to the features that HTP, Esab, and Miller-255 offer,
At the End of the Day, Helmet and a good gun will help a lot, If you get a used machine do your self a favor and change the lining right away and clean the rollers,