You could literally spend hundreds on this - I know I could! However, being on a budget as I am, I've had fair success with the following in the Garage. There is some expenditure of course if you are starting from nothing.
Small Pillar Drill and vice - (drill Press or whatever they are called) with a half inch chuck. Worth its weight in gold with some GOOD quality drills
150amp electric arc welder. Mig would be better as welds thin steel easier.
that's the big stuff.
Hand tools.
Variable speed 1/2" chuck hammer drill
Decent Jig saw with plastic, steel and aluminium/copper blades
4"angle grinder with discs and sanding pads.
Hacksaws with GOOD quality blades. If they are £1 a thousand on the market you'll soon find out why!
Tinsnips
G clamps in a range of sizes
Obviously hammers - steel, copper, hide and nylon.
Centre punch
Set of drifts
GOOD quality taps and tap wrench. Buy these individually in the sizes you need. Generally you can get away with buying '2nd' taps rather than taper, 2nd and plug.
Dies. As above. only buy the sizes you need.
A range of flat, round and half round files.
A good 6" vice.
I'd really like:
A small lathe and a power saw but room and finaces exclude these so I farm out turning, drilling large holes and either sweat using a hacksaw or when I buy larger steel take a cutting list and if I chuck a fiver in the tea fund the blokes will cut to length for me.
Using the above I've managed to make Sidecar Chassis, leading link forks, Gates, bit of wrought iron work, numerous clamps and all manner of brackets and plates for the bike.
Hope this helps and someone else will be along with a list of kit I'd die for I suspect