That's a bit difficult. When designing a world, you have to figure out how everything blends together. When a country is designed, you need to understand how geography plays into their culture and relationships with other countries. For example: You can have a country set up in a cold climate, but you need to be able to explain how they are self sustainable at the very least. If there is a very warlike country next to a peaceful one, there should be an explanation as to why the peaceful country hasn't been invaded. These can be through geographical means, economic means, diplomatic means, or through some magical means specific to the world.
What I'm saying is that first you have to pick something you want to focus on for an area, and build everything else around it in a way that makes sense. You can design the geography first, or you can build geography that will be convenient to some other thing. You can design your civilizations first, or you can lay them down once you build the geography. Or you can do a mix of the two, picking when and where to place what you want.
But please, most important of all, it's okay to ask for feedback on some of your ideas. No one is perfect, and if you don't have expertise in a certain area, you can ask for advice in those areas.
That's my two cents. Hopefully, this will help.