not ideal for aluminum...
If you were doing mostly steel and stainless, with only occasional aluminum, the Tigmate would be a decent choice. However, if you want to do a lot of aluminum you should buy a squarewave machine. The Tigmate (and the Miller Econotig) are sine-wave machines, meaning that they are not very efficient when running AC.
Look for a used Miller Syncrowave or a used Lincoln Precision Tig. These are transformer based welders that can do square wave AC and they will weld aluminum nicely.
Inverter based tig machines (like the Miller Dynasty, Thermal Arc 185, and HTP Invertig) are even better at aluminum, but they will break your budget.
Miller Dynasty 200DX
Hobart T225 Stick
Hobart Handler 180
Airco O/A Rig
ESAB W-200 O/A torch