Hmm if it is an RPG you plan to make then it will be quite the effort. Character customization would definitely draw furries into playing as well as quite a few other demographics

. Another draw to rpg's is the skill/battle systems as well as the story. But you don't have to get all of them down pat for a good rpg and if this is your first rpg it doesn't have to be perfect.
I would suggest that you work on character customization since that will probably be the most rewarding in terms of gaining popularity and a fun game to play around with

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The battle system make as simple or as complicated as your comfortable with just make sure it is usable. This can be anything from turn based, to action, it could be strategy like a chess board or just a basic one like the old final fantasy games. Regardless this could potentially be one of the harder aspects depending on how in depth you want to get.
As for the story it should probably be the second biggest priority since it will increase the memorability of your game. Although it can also be ignored a bit if the other two aspects are strong. If your not comfortable with the writing aspect you could always ask for help from some of the writers in the community.
Regardless of what you decide I hope that you have fun and enjoy the finished product.