ordered pt250ex to rework my bowfishing rig lots of .125 aluminum.. I am ok with a MIG, but TIG is new to me. Watched Jody videos and start off with 11 gauage aluminum looks like the way to go. Then I read over here that I should start out with mild steel. Which should I start with?

Then I was going to order some filler rod and parts. Does the filler rod have to match the tungsten size?

How do you pick the right size tungsten and filler rod?