First, they should never have named it a dredge. Total negative word. Should have called it a Rock Vacuum or Water Vacuum something that signifies no damage to the environment.
As for what size a dredge to get depends where you will be mining. Personally I would get the biggest dredge the river/creek will handle. The smaller the dredge the more rocks I have to pick up and throw.
What equipment would I take depends on how long I plan on being there and how far I have to pack-in. When I was working on the North Fork of The Yuba River in California for 5 months out of the year, I took everything I had for mining:
8” dredge and hoses,
3” dredge and hoses,
homemade trailer to get the dredge in the water off a bank
Hydraulic winch,
ropes to hold the dredge in the current.
18 five gallon gas cans,
oil
miners moss
steel slings to secure the winch.
Digging/large pry bar.
Compressor for air,
airline and regulator and face mask,
wet suit & hood.
Weight belt and lead weights.
Gold pans
classifiers
crevice tools
small sledge
chisel
Gloves
First aide kit
Clean out tub
Rock slings
Metal detector (I never used)
Spare parts for dredge engine
Solar panel to keep dredge battery charged
Small electric winch
This does not mention what I had at camp.
If it was just for a week and I’m working on a small creek, again the largest one I can pack-in.
I would need gas,
Dredge and hoses
Crevice tools
gold pan
classifiers
crevice tools
small sledge
chisel
Gloves
First aide kit
Clean out bucket
Large pry screw driver
And if the water was deep enough:
Compressor for air,
airline and regulator and face mask,
wet suit & hood.
Weight belt and lead weights.
If I thought about it more I would probably add a heck of a lot more. Camp is up to you, I cheat and take a 5th wheel trailer.