You can do almost all cutting with an abrasive chop saw and cut-off disks on grinders. For cut-off disks I have found the Flex-o-vit, "Razor Blades" from US welding seem to last 3-4 times as long as the ones from harbor freight. They are almost 2x's as expensive but last much longer and you don't have to change them as often.
Don't be afraid to by a used stick welder off KSL, There is a reason people have stick welders laying around, they rarely fail. Just be sure to get one with "DC", not just an "AC" buzz box. I paid like $250.00 (I have also found that sticks from US welding seem to work much better than the ones that have been laying around at HD or Lowes for probably years)
Also I have heard that you can get decent 110v MIG welders used, many people will buy them then upgrade to a 220v and try to re-coup some of the cost of by selling the 110v.
I have an expensive Milwaukee 4.5 inch grinder ($110.00), I like it a lot more than the HF ones, it does not vibrate my arms nearly as much, and is much nicer to use for extended periods of time.
being good with cutting and getting good fit helps a lot, take the 2 seconds it takes to grind a bevel on your edges.
The biggest thing that helped my welding was my welding table. Being able to vise-grip material to the table and standing upright, instead of working on the concrete, helped a lot.
search for youtube videos for technique.
I have probably $300-400 into this table, the feet are adjustable to level off and I made a cart so I can push it around easier. It is 4ftx3ft the top is only 1/2 thick, it was not flat and has bowed more. I have since turned the bottle jack up-side-right from this picture, I am not sure why, maybe the handle worked better, I don't remember.