well depending on your budget
abrasive wheel in circular saw
Tin snips
metal cutting blade in circular saw
Nibbler
hand held shear
Whole sheet shear
Now the first is nasty but will work ok and is fast
The snips are good too you will probably need a few types to cut across the profile or just one if your ripping but slow
the metal cutting blade is ok but you need to find one that allows THIN sheets to be cut
The hand shears ( electric or pneumatic ) work well. As do the nibblers ( have and use both) A Botch nibbler electric and a Snap-on shear pneumatic (both 18 gauge).
The sheet shears look great, They allow you to cut a fixed angle cut ( for end walls) on ONE sheet profile. If your doing a lot of buildings they look like a great too but too $$$ for small jobs and no one around here rents stuff like that.