The main issue is that MIG welding aluminum REQUIRES the use of the high-current "spray transfer" mode.
If you want to weld aluminum you need to have a MIG welder that provides AT LEAST 200 amps output. It would be preferable to have a 250 or 300 amp MIG machine, but 200 amps I would consider the absolute minimum. If your machine is less than 200 amps, you need a more powerful welder plain and simple
You also need a teflon liner, hard plastic or teflon wire guides, and a pair of smooth double "U" groove rollers. Rollers used for steel wire are normally "V" groove design. This is unacceptable for aluminum because V-rollers create fine metal shavings which will clog the liner, tip and wire guides, resulting in jams. Aluminum wire is softer than steel and thus jams and wire bucking is a problem if you don't treat the machine with care. I recommend using 5056 aluminum wire. Also you should use a fairly short welding lead, no longer than 2 meters.