I can just tell fireworks is going to be a clusterforget of "I need the wiki to understand that..." I just tried out making fireworks, and everything is relative to ingredients. So you need to know all the valid ingredients, what is compatible with each other, amounts of gunpowder to extend flight, etc.
What is actually sadly hilarious is you can make "mob-shaped" firework effects, which is just a Creeper face. To do it, you craft them with -any- mob head... Meaning in survival, the only way to craft them is with Wither Skeleton Heads... Lol, that will be a waste. Luckily the Creeper Face effect is awful, so don't waste your Wither Skeleton Heads on it.