Tig welder for a beginner
To do aluminum you need a machine that will do AC. I'm about to pull the trigger on the Primeweld TIG225X.
https://www.amazon.com/dp/B07BXHRBQ8/?tag=fabo03-20
Full featured machine that gets good reviews and will do aluminum. You could potentially get a spool gun for your MIG and do aluminum but the results are not as good as TIG. There are other TIG options in that price range. WeldProf, Everlast, AlphaTIG, Vulcan (harbor freight) to name a few. Another option would be to find a used Miller Dialarc HF. Huge old dinosaur but they work well. I had one but needed the space and sold it. Obviously Miller, Hobart, and Lincoln but they are more Expensive