Other ones I have thought about:
1. Cubchoo, Mienfoo, and Taillow(all 2 stage starters, ice beats flying, flying beats fighting, fighting beats ice).
2. Bellsprout, caterpie, and roggenrola(all 3 stage starters, grass beats rock, rock beats bug, bug beats grass. Prob the most flawed given differing evolution levels and I’m not sure how many actual bug moves butterfree learns).
3. Ledyba , Shroomish, and Cranidos(all 2 stage starters, at least similar evolution levels, Breloom gains fighting type but Ledian’s flying type maintains symmetry as flying is good against fighting and bug is good against grass, Rampardos being rock is good against both bug and flying, maintaining strength against Ledian as well, and both of Breloom’s types, grass and fighting, are strong against rock).
In case you can’t tell I am most proud of option 3, lol.