Running 800 gp it's pretty easy to get a large quantity of sand per window. You expend 200gp at a time to let it come back, but cap out when you find a +2 (or +1 if it's being stubborn) node.

Then you do the usual collectible rotation but with 800 gp you get an extra 'Extra attempt' use. Rng swings your way and it's 6 500+ collectibles in one go.