@FairWeather If you are in the Portland area or willing to drive there, I'm happy to take you out a few times this fall. I hunt the vast majority of the time at Sauvie Island, which has a well-regulated blind reservation process. At most spots, ODFW builds the blinds so you just have to touch them up instead of needing to do everything yourself. Most of my advice is based on primarily hunting NW Oregon.
Waders - if you are hiking more than about 1/4 of a mile, go for the breathable waders. Oregon rarely gets cold enough to need neoprene and you will be sweating heavily if you have to pack in for any distance. I have a pair of each. I wanted the neoprene maybe 3 times last year, the other 10+ times it was an easy call for breathable. A decent camo rain coat isn't a strict necessity, but will help keep you dry in the rain. My hands get cold easily so I have a pair of waterproof mittens for handling decoys too.
Decoys - I have 3 dozen that I bought used for a grand total of about $150. Keep an eye out on your local classifieds - good deals will pop up.
Some people use spinner decoys. The electronic ones (like the mojo mallard) are illegal in Oregon so if you get a spinner, get a pull-string version. Jerk rigs to introduce a bit of motion can be good too. Inexpensive ones will be around $20, or you can probably rig up your own with some old fishing equipment and some elastic and cord from a craft store.
Gun and ammo - 3" is plenty. Let the birds get as close as you can. I used #2 and #2/4 stacked last year for duck and was happy. Size up for the big Canada geese but cacklers are basically mallard-sized. Make sure your choke will work - steel can damage your barrel if you are using too tight of a choke. You typically want as tight as you can go without risking damage to your gun. I had a rough time finding 12 gauge 3" #2's last year, but ammo stock seems a bit more reliable now. I had a choice of a few different brands last time I went to Sportsman's. No need for the $80 boxes of bismuth, the $25-30 boxes of steel shot will be fine.
Other strategy - everyone else hit on this already, but the three main keys are to hide well, be in the right spot, and don't do anything to scare them off (I'm very guilty of poor calling, myself). Let the birds get as close as reasonable - I see a lot of guys start blasting from 70 yards away and they'll cripple one bird after 10 shots. You'll cripple fewer birds and use less ammo if you can hold your excitement just a bit.
Side note - Depending on where you are in the state, goose can be a bit of a pain due to the restriction on dusky geese. If you are goose hunting in an area with duskys, I'd strongly suggest going with someone experienced who can help identify the ones you shouldn't shoot. Check the regs to see if you are in a dusky zone and if you need to take the goose test and get the NW goose permit. Shooting light for geese is also different in the NW permit zone (goose light is about half an hour after duck - check the regs for specifics).
Safety - Things happen fast in a duck blind. If there's anyone in another blind close to you, be wary of where they are. When hunting with someone in a blind, take some time to clarify who shoots when, who calls the shots, and if you need to stick to a specific shooting lane. Be extra careful of loaded guns whenever anyone is outside of the blind or there's any movement within the blind. Guns can get knocked over easily and wind up in unsafe positions.