The breather setup RCM sell ( or purchase via Lateral ) is a complete package.

It works and is pretty much fit and forget. But no, it isnt overly cheap.

If a system uses 2 tanks, it is because of design flaws in the primary tank, because it doesnt actually prevent deposits getting spewed out. That may be because of bad design, or limitations due to space or other reasons. Although if the latter, move it to where there is space instead.

A proper setup will have adequate volume, good oil/air separation so nothing but air comes out the "vent" and would have a drain back into the sump below oil level to return any oil collected.

And pretty much any of the stuff you see on egay, is complete and utter useless shite on every count, other than perhaps being shiny.

An even better and fullproof design would have a filtration system inside. But good internal baffling is usually sufficient.

Actually a good well filtered design here, although it does still lack a return to the sump, so would need manually drained/cleaned

http://autospeed.com/cms/A_111060/article.html

And you dont need to understand how they work. Just buy the RCM one that does work.

Although it really is an incredibly simple thing

You want air to pass through unhindered. You want any fluids to be caught.

There is nothing difficult to understand