I managed to passed the MB2-714 CRM 2016 Customer Service exam today. It was pretty challenging. All I can recommend is pay close attention to what the exam page says will be the topics and study up on those topics. Neil Parkhurst has published a great series of blog posts summarising a lot of the key content for CRM functionality in these areas and I suggest they are well worth reading in addition to watching the official eLearning material if you have access. CRM Tip of the Day has some pretty great videos that may be helpful to you too.
I'd also suggest spinning up a CRM Online trial and working through some of the functionality as you read about it / watch videos about it. Nothing like actually using it - think abstractly about scenarios you might need to implement for a customer.