It's important to have a nice apartment generally but I think having a bedroom that you're proud of is particularly important because it represents you from a personal prespective and demonstrates you have your shit together.
Learning the basics of home decorating and interior design go a long way to improving each space. Typically, the three essentials for amateurs are adding art to the walls, a rug for the floor (of bedroom or living room) and some plants. If you add those elements, the room is going to look awesome. Here's a guide to improve the interior design of your bedroom
I think starting a hobby is important but I don't think the actual hobby itself matters too much. The importance is in how you dedicate your energy and time to something productive and doing your best each time you do it. There's a certain aura that surrounds people who are really good at something, even if you don't care for the hobby yourself.