If I am struggling with a cluster, sometimes I will open a new document and add the elements I want to put together on there. Then I group them and move them to my layout where I want them, play around a little more (resizing or moving) and call it good! Many times when I do it this way, I will save it as a cluster in the kit I used too, so I have it again when I go to use that kit another time!
Also, templates with clusters are my best help! I use them as a basis when doing my clusters. Sometimes I will add, subtract or move something, but it is a good starting point!
Keep playing and trying, and you will keep getting better and better!