I have written the certificate exam and I can tell you its not walk in the park. Besides basic training you need to have a very good understanding of security concepts as well. There are a lot of question on MAG and portal too so dont just focus on gateway. I suggest writing the basic exams through partner portal that come after every course and then review security concepts e.g., SSL, certificates , identity, federation etc., Although format is MCQs there are lot of similar answers and make sure that you have done couple of installs of gateway, portal, MAG yourself before your first attempt at writing certificate exam.