It will be difficult to handpick a few important topics. Law of obligations (Part B) is one of the most important areas to understand in terms of spirit of this paper. And that has a lot of weightage in the exam. Most candidates feel the company law portion (including the formation, dissolution and administrative affairs of organisation) to be difficult than other areas. And last but not the least, "GORAS" have special interest in fraudulent and criminal behaviour, so get yourself familiar with the relevant material. Moreover, it is relatively a new addition.

Either tax variant would be fine, depends on your goal. But do consider the fact that, unlike Pakistani variant, relevant technical articles and study materials are easily available for the UK variant. Not really sure about what is preferred in the Middle-East, generally only local tax knowledge (wherever you work) is respected.