Best to just buy the gussets pre cut can't beat a shear for that
many place just cut them from left over plate rems.

for everything else horizontal band saw.
change your cut order cut the angle first then cut to length
for a short angled piece of tube.

it's a mater of using the right tool for that particular job.
then you can get into the good stuff like a cnc plasma table
you can really do a lot with that