Hello.
I am currently new to GMAT and I am wondering what guides / books are good to study alone. As a university student, I do not have any money to invest in the materials so I wonder if I can get any free resources. Currently, I have
Manhattan Prep 2012 edition and some of the 2016 edition. But I wonder if these books are enough and not outdated as it has been almost a decade since released. Are there any major changes to the GMAT exam formats within this one decade?
I am also doing the GMAT Official Guide and currently around 300-400 questions. But I am doubtful that this guide is enough as the questions in the guides are basic mathematics. Will the test be on a similar level or more challenging?
Lastly, may I know where I can get free GMAT mock tests?
I understand that I need to invest some money to get good materials. However, due to my situation, I could not. So I really appreciate the help from you.
Thank you so much for your advice

.