>>96062311
Lets talk quests for a minute because you're asking big questions and we'll get very lost if we don't focus. Here's a very basic quest structure: Inciting Incident -> Resolution, that's one you're describing. The party is activated to go do a thing, they do the thing and come back. A way to make that type of quest more interesting is to change the structure to include a layer of complication that changes the basic problems that need solving or makes the players reevaluate their initial assumptions about the case. Ideally, the complications should give the players choices to make. In your example, what if the ring is full of bad mojo? Does the mayor know? Why is the ring like that? Did the mayor seem sketch or is that just retrospect? What would giving him the evil ring do for him (or to him) and the city he governs?
A neat thing about the model is that it's very scalable, from a tiny one: There's rats in the basement, BUT they're walking and talking, or a big one: The players have to defeat the evil empire, BUT the evil lord is one of the player's dad!
Remember, keep it simple so it's easier to remember and allows for more improvisation.