Ride every day that it is possible and park in the garage at night. No cover. It gets a bit dusty if I dont ride for a few days but its a motorcycle, mechanical pieces of metal after all.
I got an HD cover for mine while I make room in my garage... but even out of nature I see myself putting the cover on it in the garage... really doesn't take much effort and keeps anything off it.
I'm shopping for a cover now. Bed sheets work great in the garage but at work it sit's in the sun baking. Not to mention dust and pollen. Yup a covers in my future.
I keep mine in a shed and at first had moisture issues...had to put in a small window that I keep open about an inch. Also cover with a painters drop cloth.