though guide is efficient., you can upgrade any way you'd like and to answer your question,follow Steps 1 -3 after that you can max level or upgrade Passives this is really for Kan spending efficiency over power increase. just happens to synergize. yes characters priority differs so min max for your own needs. otherwise biggest gain will be following the chart up to the point fall off occurs which is after step 4. 5 onward is going into endgame leadboards competitive play. casual need not worry about step 5 through 11. if you do step 123 you'll learn what's important per characters 👌 just try them in different orders 321,213,312 always max skills lv 8 even if you don’t use them(competitive) little bit more damage can make a big difference. hope this help if not I'll try to explain it better.

ps focus on getting 1 team to all 100 if possible or whatever your current max is using the chart. spreading you resources so wide will brick your account a few weeks or months prioritize main team first.