plumbing is going to be costly, tips, hoses, pipeing, fittings. will run up fairly fast.
TIP: a chunk of 2x4, cut a V notch in it. + drill press + a couple clamps = a way to drill a variety of size pipes. this would be more for thicker walled pipe and screwing in some spray tips.
barb fittings + hose + misc other fittings more likely cheaper alternative.
you want a way to adjust the boom height from ground level.
spray tip nozzles for booms, pay for the little more expensive tips that have a "little valve adjustment" on them, and some sort of #2 pencil size filter in them. granted it is not that many acres, but when tips plug up you will be whining about it for some time trying to get them unplugged. and the little valve on them most likely needed, as in you will get one really putting out, and maybe another barely putting anything out. the valves are a needed requirement.
2x4 most likely easiest thing to mess with, as far as drilling and/or attaching some clips to hold hoses and spray tip nozzles. you do not need a metal boom pieces.
your spray tips require a certain amount of GPM to work correctly. and will more than likely determine how many spray tips you end up using.
if ya not to experienced with misting and spraying, you can create a lot of un-necessary misting that just blows away. the spray nozzles with exchangeable tips can be a bit costly. but the different type of tips can be fairly cheap.
for most part everything going to end up being cheap plastic.