Ordnance Guy
You say your aim is TIG.
What no one has said on here is what colors to get when welding.
If your welding aluminum porosity can be common good gas coverage needs to be adhered to to obtain good welds. Clean everything with alcohol and use new gloves. Any contaminates will compromise the weld zone and weaken it. Also sheet aluminum comes with what the industry calls "Alcad" this is a 99.99 percent pure aluminum. This does not weld good and has no weldable properties in it thus removing it mechanically needs to be accomplished for a good weld. 6061 is the best weldable aluminum and intended for welding, 5052 and some 3000 series aluminums can be welded to but are not structurally sound when welded.
When welding ferrous metals certain colors in the weld zone after the zone has cooled need to be adhered to also. Silver is the best it means you had perfect gas coverage and speed, light gold is ok, gold is ok, a very very light tinge of blue is ok, anything darker than the light blue is contaminated with impurities.
If you can acetylene weld you can probably tig weld as the method is the same. It takes some time but the welds are very good.
No one has mention penetration. Cold welds, welds that have excessive undercut, and welds that have porosity in them are weak and usually don't have the needed penetration.
Try practicing on plates of metal until you get a bead on both sides. The bottom bead will look horrible if you don't have back-up gas but it will suffice for most of what the folks on here are welding. If you need it to be a clean bead on the back side they sell paste you can apply on the back side which will protect the weld zone from impurities in the air and give you a decent bead.
Welding is a science and can be a great hobby as well as a great job. I enjoy welding a lot and can give you a few words of advice.
First do not scrimp on safety gear. Second clean everything your welds will show your craftsmanship and everything else if you do not. Third grind bevels where needed and grind welds where needed. If you end up with a weld that looks like a bird crapped on it then grind it out and redo it. Fourth gas coverage in any of the welding practices must be adhered to closely.
And if all else fails "grind er and paint for the welder I ain't" comes to mind