LOL, Perfect God 101 (for Catholics at least)
A god imagined "wanting" something means that god "lacks" something, which means such a god is not Perfect in whatever detail/attribute/thing is imagined to be "lacking". Which then means on can imagine a greater god that does not "lack" whatever this imagined lessor god lacks. So if one's view of God imagines that He needs something, anything - then one has not imagined a big enough God and need to think bigger.
To say God wants and then acts toward achieving something lacking also means God improves by obtaining whatever "want" is imagined, which means God changes, which must mean God is not Perfect in whatever aspect it is imagined that He has a "want".
God created man to love, serve and know Him. We could reason some similar purpose(s) for His having created Angels. It does not follow from saying that, that God needed (before creating us) or needs now our love, service or knowledge of Him.
God is. Which means, among other things, as the only uncreated Being His ONLY purpose is "to be". Such a God does not have wants or needs. If a sentient being has wants, needs, the will of such a being can be directed via the intellect toward achieving/acquiring a want/need. His Perfect Will acts towards ONLY one thing, the Supreme Good. Which is Himself, which in every sense He "has", because He is the Supreme Good. So God cannot be understood as "needing" more Supreme Good, which would be required if we said God needed something.