So how do I know what universities want? Start by reading about the university, the course you want to study and the "entry profiles" as these will give you information about the type of student the university is looking for. Universities also want the truth so do not lie about your abilities and they want your writing so do not ask someone to write the personal statement for you. Some areas to cover include why you want to study this subject, what your future career plans are, what you do in your free time, what skills you have (academic and non_academic), what's interesting and/ or different about you.
In some ways you are very lucky because your experience of high school, hobbies and life experience will already be different from many UK/ home students so you should take advantage of this in your personal statement. But you also need to make 2 things very clear. Firstly, why do you want to study in the UK and secondly, you need to show that your English is of a good standard (usually IELTS 6ǌ or above). It is no good having IELTS 6Ǒ if you personal statement is full of grammar and spelling mistakes. But DO NOT pay for someone to write your personal statement for you on one of the many websites offering this service. If you have IELTS 6Ǒ, you do not have perfect native speaker style English and universities may reject your application if they suspect it is not your writing.