Keep in mind the metro was car #2 I tried building. The first one was a bit more rough
It does take a bit of practice getting it right but the good thing is the metal is not that expensive really so it won't cost much to abandon a car and start over.
For welding I say use what you like. As long as it is a good weld it really doesn't make that much difference for most things. I used a gasless mig for 90% of my frame and a stick welder for the rest of it. I would have preferred to use a stick on all of it but the mig is so much easier to get a good weld with it was a matter of convenience to just use it.
Off the top of my head here is a list of stuff I have for metal work. I will probably miss something but it will be a good start.
Welder - lincoln pro-mig and lincoln ac buzzbox stick welder
cheap chop saw from Lowes
Angle Grinder came with it in a package deal
Tubing notcher from harbor freight with hole boring bits from Lowes
Bender from harbor freight
alignment magnets from harbor freight
hobart airforce plasma cutter
lots of jack stands probably 12 of them total. Useful for holding stuff up. Can also weld them in place to keep stuff steady.
That is about it and it has done a pretty good job for what I use it for.