Either you don't have ritual monster in hand
Or you don't have a normal monster in your deck (for Advanced Ritual Art)
Or you don't have monsters in hand or field whose total levels EXACTLY EQUAL to level of ritual monster
Just want to clarify. I have a magician of chaos and the advance ritual spell. I dont understand why i cant use the spell even though there is a level 7 monster in my deck.
That's less because it wouldn't be useful in most Ritual Decks, and more because Cyber Angels are the only relevant Ritual Deck (aside from Magician of Chaos now I guess), and need to Tribute things to work.