Personally I prefer a good AC/DC tig/Stick machine for all round convenience. Big stuff only limited by duty cycle; small stuff and odd metals are only limited by your setup and ability to see. I definitely recommend either signing up for classes or alternatively being friends with a weldor. Either way you will be able to learn from and find the machine that will best suit your needs.
Another thing regarding the different processes is;
MIG : Have to have shielding gas coverage and is best used indoors. a lightly breezy day will blow the gas away and the weld will be poo poo.
Stick and flux-core (SMAW & FCAW) respectively are fine for outdoor use stick more-so though ( my personal take on it) Flux-core sometimes will depending on the wire you get, may be a dual-shielded variety and will need gas too so breezy outdoor welding is out as well. Stick can be used in fairly windy conditions if the need arises.
TIG: I love it I hate it. Slower than the other processes but the welds are beautiful and can be a pain to learn. best done indoors comfortably as possible and calmly as possible. This is a very hard process to get halfway right and to learn it you will learn to get some of that Buddhist monk zen feeling :cool2: or frustration will drive you up the wall :mur: . I hate it and love it.
Now for the kicker. Once you have figured out how much welding you plan on doing ( occasional or lots ) find a machine that will do what you need and get it. A bigger machine is more powerful and can weld longer without a cool down (duty cycle) but is also more spendy. A smaller machine can do big things if you know what your limitations are and the machines and work within them. The thing is it may take longer to get something put together correctly ( multiple passes, preparation, etc. ) but will keep the budget down.
Consumables are something you need to look at as well. Stingers, MIG gun liners and all that stuff. Many folks are ordering online now but when that project has to be done today online ordering can't cut it so find a LWS that you can build a working relationship with and that will help alot.
Always keep a fire extinguisher close even three or four ( please don't ask :laughing: ) If it smalls like hair (clothes, leather) burning it is. :confused2:
I'm gonna end this long winded post here. I usually lurk unless the topic is something I know anything well enough to contribute to ( rarely ) but fortuneatly welding is my bread and butter. Good luck and have fun.