Reddit mentions of ELT Grammar Book: A Teacher-Friendly Reference Guide (Alta Teacher Resource)

I didn't fail the first time, so I think there's hope for everyone. The test is the easy part! Of course, since you're being compared to everyone else taking the test in that cohort, you could be a total rock star and fail or have a bad day and still squeak by.

The official study guide is a good source for all the sections. Since I've always done well at English, I didn't study for it, but I imagine that GRE/SAT study guides might be of some use. I don't know if it would be of much practical use for FSOT studying, but one of my college classes used this book and I felt it was very good at elucidating the hidden rules of English grammar.

Last time I used the app, I remember the questions seeming more challenging than the actual test. There's tons of free college courses online (Coursera and the like) that might help you improve your knowledge. While I think finishing my MBA last year helped, I feel like the breadth of the subject compared to the number of actual management questions probably doesn't make it the most efficient focus of your study.

I'd say effect and purpose is plenty of knowledge for the amendments. No need to memorize verbatim.

Good luck!