Do Yourself a favor and get a MIG Welder with at least 250 in the Model # (scales with the thickness in mils (.001") for material) along with amps available from welder and get a spool gun to go with it. TIG welding aluminum is difficult and doesn't get any easier once You learn how. What do You want to fabricate?

I want to build up the normal stuff. Intakes, gas tanks, linkage, stuff like that.

I completely disagree. If you want to weld fast, with limited welding skills, with little regard for weld integrity or cosmetics, mig is the ticket.

If you have patience ( why women often have great tig skills), are willing to practice, and be rather anal on cleanliness ( solvent cleaning, ss sire brush right before welding, brush the tig rod, very clean gloves, etc) Tig is the ticket.

A comment was made earlier about 100% helium, that would not be a good suggestion, I often use a 80/20 Argon/Helium mix as it has better heat for thicker alum items. I use a 625A Miller Syncrowave Tig, my mig machine is used 98%? for steel.

Cover all your exposed skin, skin cancer is a [censored].

OP, I see worthy progress, be careful about grading your own welds until have broken a few.

I have been brushing with a SS brush, but it was a Harbor Freight piece in the $1 bin, so quality might be questionable. It seems that there are a lot of personal choices on gas. I'm guessing that a lot of it has to do with technique. I have been using straight Argon, but also have a Ar/CO2 mix that I've been using for my Mig. Maybe I'll try using that.
I immediately noticed that welding steel is a very quiet, gentle process. Aluminum, I'm guessing it has to do with using A/C, is very noisy and seems to be a pretty angry burn. At least it's my perception. I think I'm backing out of the pedal to make it feel like welding steel, but what I am really doing is killing the heat and losing the puddle. I need to learn how to "Stay into the gas pedal". Lol!
And another thing I noticed, aluminum might dissipate heat faster, but it sure does transfer the heat to the rest of the material faster. I can feel it pretty well through the gloves.

I have been using straight Argon, but also have a Ar/CO2 mix that I've been using for my Mig. Maybe I'll try using that.

Don't do that !!

To get the ball tip on the tungsten, sharpen the tungsten then hit the power with it over a copper penny. Bring it straight down towards the penny and the tip will ball up. Now you're ready to tig aluminum.

I'm welding on 110 volts. It has a 220 volt adapter but I didn't get my garage rewired yet. Welding at 120 amps. Pulse turned off.

When I went to the Lincoln Motorsports Welding class (week long) they taught us sharp electrodes for inverter machines. I have a Lincoln Precision Tig 225 and use pointed electrodes for aluminum.

Yes, same with big blues.. The grey electrodes work well with any metal on inverters, I haven't touched red or greens since I sold my synchrowave.
Acetone is your best friend when welding aluminum, the more cleaning action you use, the less depth there is to the weld and the the less concentrated the bead is. I wipe everything down with acetone, and as others of said, stainless steel brushes, that only get used with aluminum and nothing else. I even have a set of gloves that I use for specifically for aluminum. I got my Tig training in Japan, with a guy yelling clean clean clean in my ear for 2 weeks..
Forget about that caustic stuff they sell in welding stores, doesn't work..

I use blue, 2% lanthanated for steel and aluminum.