A lot of the targets I see are either really cluttered or just plain difficult to see at distance.
Sometimes I'll buy a bunch of targets only to find that I can't really make out a good point-of-aim once they're out there. This makes it very difficult for me to shoot for groups because my aim is inconsistent/not small enough.
I also don't like shooting at circles. Shooting at grids is best for accuracy IMO because they're easy to line up with your scope's crosshairs/stadia lines.
So I made a bunch of bold black crosses and put them over a grid of squares. They are 30 squares by 40 squares, and if you fit these images to a standard page of paper with 0.5" margins all around, the squares are exactly 1/4 inch, so you can easily measure MOA. I made a few of varying sizes, feel free to change them up however you like.