Jeff,
First of all, given you fairly modest power goals, I'm not sure you really need WI. That said if your local pump gas is low octane rated, you don't think your current injectors are flowing enough or you just want some of the additional benefits of running WI, I don't really think you need to get too complicated here.
I don't want to get into a major discussion of whether various kits on the market are overpriced, value for money or whatever. This is something you really need to decide for yourself. When you buy a kit, you buy convenience because everything you need comes in the box and saves you the trouble of going here, thee and everywhere to get all the components.
However all things said and done, a WI setup in it's crudest form is composed of a reservoir, a nozzle, a pump, hoses and a means of activation (boost/pressure switch). You can get the majority of this stuff dirt cheap.
After that refinement comes by way of inline check valves to stop water dripping into the intake off boost, low water level float switches to tell you when you are running low on water etc. About the only thing I would say you should really buy top quality for is Nozzles and aquamist are generally considered the best.
My advice?
Get a Shurflo pump. If you aren't going for a top end system with fault diagnostics (what Ken Inn calls the 'anal' setup) the Shurflo pumps are pretty much the best. Run forever, won't burnout if run dry and have enough pressure to pump water all the way from a trunk mounted reservoir if required.
Get some aquamist nozzles (but you'll need a special tap to fit them !!!)
Pick up a big windsceen washer bottle reservoir and bracket from a junkyard.
Get a simple pressure switch that activates around the 8-13lbs mark.
Put the nozzle about 2 inches before the elbow leading into the throttle body to allow atomization before water is drawn into the cylinders.
Finally a word of warning. Tuned correctly, the WI should allow use of higher boost on low octane gas and/or the ability to run a leaner mixture without detonation. If your WI stops running for whatever reason ... clogged jets, reservoir runs dry, hose pops off ... you will be running LEAN which could be catastrophic.
So 'consider' putting some failsafes into the system to detect any possible problems or install gauges and be aware of the warning signs they give such as higher EGTs.
Paul
Speak to Ken Inn as well ... probably one of the most experienced WI users on here. I talk a lot of theory ... Ken speaks from experience !!!