Copyrights went up to $40, I thought. I copyrighted Muley as a cartoon, puppet, and costume, including all his co-horts in hilarity. Trademarks range in prices, actually, from $100 to way-high.
When you create something, you are the author and hold the automatic copyright; but, by filing with the Library of Congress you have legal ownership that can't be argued or denied should legal recourse arise. I created Muley and friends as cartoons in 1980 when I was 7 years old, one of my comic strips were stolen for an advertisement when I was 9, but I never got copyrighted until 1988.
Don't rush into it, just keep photos and all that in case you need it. When you get finalized--closer to your product--then start worrying about copyright.