I started a different project first and originally wasn't a plastic canvas fan. I was using a needle that was too big and I started with a huge project with large areas of a single color.
I switched to the blocks and played around with different stitches. Plastic canvas is nice because you can stitch it go quick. For large areas you can stitch over multiple holes instead of a normal stitch of doing just one. I found that cotton yarn was the perfect weight.
But I think the needle made the biggest difference. I was using a big one that worked, but it was a pain to pull through. I went and bought one specifically for 7ct plastic canvas and it was so much easier!