All the skills are important of course. Assuming you want to reach a high level in a language, and a high level in each skill, you will need to spend more time in some areas than others. Listening and vocabulary acquisition take the most time, so you are probably on the right track if you devote more time to them.

I think all the skills are important, they complement each other. I can't speak with other person if I don't speak correctly ( more or less, at least) and I can't reply what that person has said if I don't understand him. Besides, if I don't read, I won't learn any vocabulary and my grammar would be a mess, so I won't be able to express what I'm thinking while I'm writing. Everything is important.

I will say I think it is very important. I am learning french and i emphasized reading and speaking over listening and I am still struggling with listening skills. If you can't understand what someone is saying to you, what good is a lnaguage?