Crochet

I am quite a beginner, and this is my first 3D crochet project. I fell in love with Marrakesh-style lampshades but couldn't find a pattern, so I tried to figure out one based on the general instructions from this page (project 5). The shade is worked entirely in single crochet using a 50/50 cotton/polyester macramé yarn. It has three metal rings crocheted directly into the fabric for structure. I kept things simple: whenever I increased or decreased, I always did it every 12 stitches. To change the angle, I alternated increase/decrease rounds with plain rounds, but I feel the profile could be smoother. The next version will be made with 100% cotton yarn. I'd love some advice on shaping. Is there a better way to decide where and how often to increase or decrease to get a smoother shape? Right now I mostly guessed and experimented.