I have a stock 350 horse 440 with Hooker Competition headers and a Holley 770 Street Avenger carb. The ground straps are ghost white on the tips, fading to a more greyish white towards the bend of the ground strap.
I heard that these were lean out of the box but wow.

Firstly, how many jet sizes should I step up to start with? I was thinking step up two as a start and go from there. I'd like to take this thing apart as few times as possible.

Secondly, are the gaskets supposed to be reuseable or no? I had heard that Holleys come with "forever" gaskets that are supposed to be reusable, but somehow I think that is bologna.

I can tell you in my 360 with a 3310 750 VS holley I run 76 primary and 82 secondary jets (did the secondary metering block conversion which the 770 avenger already has). I make about 340 wheel horsepower, but otherwise I'd think you should be able to run something like that to start with and go from there.

As for the gaskets, if they're the blue neoprene type, so long as you don't damage them you can reuse them over and over. I'd recommend getting the Moroso bolt washer gaskets (little plastic ring gasket under bolt head) for the float bowls unless the Avenger already has something like that as well. Then no gaskets to replace each time you open it up! I also highly recommend the Russel Fuel Inlet kit as you don't have to remove it to pull the bowls, just unbolt the bowl and let it flop a little out of the way (obviously catching the gas somehow too..). Hope that helps!

Not sure how much to jet it, but a gasket trick is to coat the gaskets with chapstick. The wax helps keep the gaskets from sticking.