So in my own craft I use some....unusual, I guess you could say, ingredients. Some are just things I can get my hands on through various circumstances and others are household items that I think many in the craft don't think to use but due to my time as a closeted witch I had to get a bit creative. And now I'd like to share these things with everyone :D
Specifically these are ashes of bills and other papers we receive that contain sensitive information we don't simply want to throw out for obvious reasons, but I also have ashes from incense and other things.
Ashes can symbolize rebirth, as the legendary phoenix rises from the ashes when it dies. Also ashes are basically something that was a thing and is now just in another form, a sort of symbol of transformation. Not always into something beautiful, or something you like, but something necessary.
I like to use ashes in spells relating to those two things in general. But I also like bill ash like this for spells related to money (specifically reducing our bills) or related spells because they still hold that energy even in ash form. I would say perhaps even more so because of the added energy from the fire used to burn them.
And of course, you can use ashes for cursing. Curse someone to never escape their bills, or to have a life as colorless as the ash itself. Heck, a Silent Hill based curse would make great use of ashes!
Hopefully that has given you some ideas, and please remember to practice fire safety. Only burn things in designated areas (fireplaces, fire pits, ect) or fireproof containers, always have water on hand just in case, and if you're burning indoors have the area be well-ventilated, especially if you have pets or people with respiratory problems!