From someone who has been welding for about 50 years- before you take another damned step go to your local trade school/junior college what ever and take a class. Don't run out and buy a bunch of second hand crap you haven't got a clue how to operate and may not need in the end.

Go to a few local welding shops and ask the professionals. These guys will give you straight answers on what you need for what you are going to do with it. Try auto body shops also. They deal in thin metal. They will recommend a MIG rig but will tell you which ones last and what they should cost.

Get a oxy rig. I doubt the ones from Harbor Freight are worth the effort. I have 2 rigs that are over 40 years old and still work perfectly. If you buy one second hand DONOT buy the large industrial size bottles. These bottles are OWNED by the gas company whose name is on the bottles and are only RENTED, never sold. If the seller tells you that they can be sold take them to the local welding/gas refill place and ask if they can be refilled. I'll bet that they can't. Ask them what kinds of bottles can be sold and what they look like.