Not sure about Gasless MIG, But certainly I'd go for a MIG.
I use my wee 130 with pure C02 (Pub Gas) with no problems, and a lot cheaper than the small bottles from the shops.
Some will argue its use, but I have used it for years, no problems.
If you have pleanty cash, or work with exotic materials get a TIG. - Too fancy for me.
Like I say, I have a wee 130 Turbo Snap On MIG and it gets some torture. Wire feed roller bracket (small plastic bit) sometimes gives up, but easily replaced.
Happily weld tin sheet, or reasonably heavy steel.
Cheaper ones are available, but like most th