veganbikes

My jacket is waterproof and has some air permeability. I got the Chinley 3L from Mountain Hardwear. I liked it because Gore-Tex doesn't quite have the instant air permeability but MHW's Dry Q. Elite does, plus this one has pit zips a chest pocket and two handwarmers. However there are obviously people who disagree and working in the outdoor industry there is fierce competition and debates. Spray on coatings like what TNF uses in their HyVent and you will find on other similar cheap jackets just cut down on breathability and wear out quickly which doesn't help anyone.

My previous shell is/was a RAB ShellNeo using Polartec's new NeoShell membrane which was great aside from the zippers that RAB used which have been failing on me (NeoShell is awesome and there are probably some much better jackets on the market with it mine is two years old)

Basically waterproof is garbage if it doesn't keep you dry on the inside. If you are sweating a ton then why wear the jacket? I would rather be soaked with water than soaked with sweat (unless really cold out). However yes I do understand a good rainshell is several hundred (at least) but consider it as an investment. I will have my jacket hopefully ten years down the line and still be using it which comes out to 35 bucks a year (MSRP of $350). So big initial but you break it down and it isn't that bad.

If all you look at is price than don't bother with anything outside of what Null66 said, a garbage bag because with cheap-o jackets that is sort of what you are getting, maybe just a touch nicer. D.I.Y.ing waterproof jackets is a bad idea it will only end poorly and with a less waterproof jacket. I dig cheap and I dig D.I.Y. but especially here I would rather get really good quality gear that I can have for many years to come.