You can graduate the depth to the areas you prefer the substrate and leave less in areas without need of it where the it doesn't have plants.
My thoughts are for creating a softer sand pool in an area of the front and more space for the stones toward the back on my new build. That same might work for you as well.
Sand blasting sand is pretty clean /lower dust than construction sand, you might find it for a really reasonable price. Ours is around $17.00 for 50 pounds. Pond filter sand is said to be pretty good but very fine I think. Kids play sand is supposed to be lower dust to avoid silica dust from my understanding.
More options to get the substrate built up economically. Maybe you can find some good ocean sand and sift to the desired particle size.
The tank looks nice, very colorful with plants and fish.