If I was the op for what you want to do and the price go for gas less, I have just ordered a tig welder to teach myself to tig and just the gas is around £100,

when I was younger my only welder was arc because it’s all I could afford, I ended up welding wings on with it, body repairs and made a few straight through exhausts for mates for a few £££ back in the 90’s, A flux cored mig was a step up

there are a few videos online showing the difference and on thicker material the flux core actually penetrates the metal deeper,

if you take the flux core option you can buy different wire thickness, like all welding just make sure you prep