cipher - 220 black squares (but that's not the point)

_{Some hints for this question have been embedded in this challenge: Counter-Red Spiders.
...though that is a standalone puzzle.}

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The title technically describes this puzzle. There are, after all, four grids here outlined in black. Each is itself a square from which you can also make 4 4x4 squares, 9 3x3 squares, 16 2x2 squares, and 25 1x1 squares; for a total of (25 + 16 + 9 + 4 + 1 ) * 4 = 220. But that's not the point. There are 900 black rectangles, but that's not the point either. Honestly, it's just a title; it had to be called something; and the puzzle per se has a lot of elements in it, but they are all meant to be discovered, not spelled out.

Obviously there's a cipher here somewhere; figure it out. If you need hints, they're already included in the puzzle.

I will tell you this... the solution to the cipher is a piece of advice; but it's really terrible advice as advice goes. It's just themed. I'm not here to change the world; I'm just here to entertain some wary traveler for a while.