[TheHolyHades1]

My team has access to a waterjet through one of our sponsors, so we send out a fully laid out dxf and stock to get turned into gussets with fairly quick turnaround. It's basically as easy as lasercutting, and significantly cooler.

If that's not an option, a few ideas come to mind. They'll vary in their effectiveness based on how precise the parts need to be.

1. If you have access to a tabletop lasercutter, you can cut out gussets from cheap material such as 1/8" plywood, and then transfer holes onto metal from there. Use a mill to cut out the profile and drill holes. This will obviously be the most precise, but also the slowest.
2. Using the above method, you can also probably use a hand drill to do the holes, since you'll have them punched. Then, use a bandsaw / jigsaw to cut out the shape. I'm partial to a jigsaw, myself.
3. Cut out a shape for the gusset from stock however you want, and then clamp it directly to the pieces that need to be joined. Drill through both the gusset stock and the material to be joined in one go, rivet / bolt, and repeat. Your parts almost certainly won't be interchangeable, but it'll might also be the quickest method.