To this advice is the added element of Higher Level (HL) or Standard Level (SL); this doesn’t always equate to a degree of difficulty, but is a distinction that is often made in terms of prerequisite subject demands for university entry (most commonly in the UK). This requires some research on your part and we have provided links in Firefly/Secondary/Higher Education to help you do this.
Nevertheless, the two criteria of aptitude and interest should take priority as they did in your IGCSE choices and you should remember that Years 12 and 13 are not just a ‘means to an end’ but are two years of your life in which you should enjoy your studies and experience success.