Research is more important than you imagine. Especially if you plan to write something.
No matter if your world is magic-oriented, people want to read things that make sense. In my browser history, you'll find everything from how long it takes a corpse to decompose, to how blunderbusses worked and the parts of medieval armour.
I wrote a scene where one of my characters teaches another to shoot an arrow from a bow, which meant heaps of research. Your larger demographic probably won't know all out every subject you write. But there will be those who do understand the inner workings of it. And while you'll probably never be 100% accurate with everything you write, as long as you have the base down, it'll be OK.
Why is this important?
Well, you DO want your story to be believable, don't you?
Included in research, I like to throw in things like character sheets and maps.
You want to know your characters before you begin. Their flaws are important too. You want to map out beforehand how they're prone to react, what they like, love and hate, how you plan to have them grow and what they should achieve. Important here is also their physical appearance. Make sure to write it down and consult it when you describe a character. This will prevent them from looking one way the first time you encounter them, and a different way the next.
Maps. You need them. This will help you plan the route your characters travel, if they travel. It's great when you can add a scale to it. It'll help you know your world, plan out where you want big things to happen and work on distances. This may sound stupid, but distance is fairly important, especially when characters will travel.
If you can work out that it takes a group of fit people about a day's march on foot to complete 20 km's, you can calculate how long a journey of 500 km will take, for example. Then you can accurately say how much time passed on their journey, throw in some days for battle, subtract some when they get to horses etc.
The point is this, especially while you're planning, but also while you're writing, you need to research everything you can. If you know what you're talking about, your book will be much more believable.