I'm just a white belt, but I might be able to help you out with this.
Some important things for white belts would be: Defending submissions (this will be the first thing you will learn probably because after you get submitted with the same armbar a bunch of times, you probably are going to figure out how to avoid it)
Passing the guard (knowing how to break closed guard, keeping your base so you dont get swept, knowing a few different guard passes and what situations to use them in)
Hip movement in guard: this is very important to get this down, because your hip movement is a HUGE part of your guard, so you must get used to moving your hips around in reaction to what your opponent does
Escaping side mount and mount: LEARN YOUR SHRIMPING, this is VERY important, and 1 thing I need to work on. Also learn the upa escape for mount as well.
Basic submissions: Armbar from guard, armbar from mount, kimura from guard, americana from mount, americana from side mount, kimura from side mount or trapped head, triangle from guard (depending on your height and body type, I am short and stalky so I dont have any luck with traingles) just to name a few
Defending the RNC: you will probably get put in a RNC a lot of times when you first start, learn how to defend this and how to get out of someone having legs in
Learn RNC and how to maintain position while you have back mount: This is another thing I have to work on, my rnc is quite poor and so is my back control.
I know I am a white belt, but I probably have more experience than you, and I really think about bjj a lot, so I think this is a pretty good list. If any higher belts want to critisize I am open to it because I want to learn too.