We get a lot of questions about welding. Once you can weld, the options for customising your bike expand dramatically.
But there are lots of options for welding equipment, at lots of different price points.
Have a look at this flow chart (download a copy here). The idea is to help you choose the welding process and equipment to suit the sort of work you want to do.

My overriding recommendation (if you are seriously levelling up) is to learn to use AC/DC TIG – and then eventually purchase a machine if your own.
An AC/DC TIG welding machine will let you weld all the commonly used materials on your motorcycle – steel, stainless steel and aluminum – with one machine and one gas bottle (argon).
With a change of machine settings and welding consumables, you can switch from one material to the other in a couple of minutes.
Anyway, if you want to pick up the absolute basics on welding, I’ve collected all my welding articles and videos and put them together in a course. You can sign up for it here.