First things first- boots take priority. Save if needed, but buy quality. I grew up hunting units 139/142 (palouse) and hunt the cascades alot now to. Im super picky with boots and have tried alot of highend boots. Every person has different needs, but I have not had anything as nice as Crispi. I prefer the Nevada and my feet never get wet. Kenetrek was a distant 2nd for me.
Pack next- dont buy junk to save. If need be, just get a used/old internal backpacking pack and put your meat in dry bags until you have enough for a kifaru, EXO or Stone glacier.
Pants- if you can do Sitka, firsrlite, kuiu etc.. that grear, but not nessasary. A pair of brearhable solids will be great. I like prana zion stretch and black diamond.
Hard shell- since it sounds like you will be on the palouse, don't sacrifice boot budget here. Check out heli hansen impertech to get you by. Then save up for some technical stuff. I love the sitka cloudburst, but firstlite and kuiu has great stuff too. If you can find some arcteryx stuff at a good price that will work. There is waterproof raingear and there is breathable rain gear. You cant have both. I always use gators too. Lots of good ones. I use black diamond gor-tex
The river breaks are the steep hills and deep draws going down to the water. Mostly private in both 139/142. Better get onx and start working on permission. We have tresspassers every year and call the sherrif or officer king w/ WDFW.