How many kg's of luggage are you supposed to take on a plane?

I am moving for 1 year to a foreign country, we are not rich so I can’t take little clothes and just shop there if I am missing some clothes. I am a person that can’t decide what I want to take with me when traveling, I always have to carry a lot of things with me. Well I’ve started packing and my bag is already full when I haven’t even put my make up and jewelry in it. I can’t zip it, it has only my sports clothes, normal-day-wear clothes and like 5–10 pairs of shoes.

How can I pack everything I need and not go over the limit of what I can take with me??