It really depends on what you want to do. Knowing Moose is unnecessary for most, to all, basic stuff. Catalyst is now Moose based but wasn't for a few years and the general code layout did not change, only the flexibility and internals of things.

Knowing a little Moose, creating attributes and using around|before|after hooks gets you 90%+ of what the average end-user of a framework will want for customization or "power-tools." Becoming more of a Moose expert in roles and such is good to have but unlikely to ever come up unless you're creating custom meta-controllers or models or something. It's also a pretty big pill to swallow in addition to learning Catalyst and whatever models and templating you're adopting.

If you have specific points you're stuck on or worried about, you should come back with details. It's a pretty wide and deep problem space for general advice.