Salut!
First thing, don't go too deep into grammar, it's not that vital for TEF, you should spend the time focusing on the 4 aspects of the test:
Listening: French radio stations and songs ( try to learn the lyrics, it's much easier to learn vocabulary from a song). I used an app called "Radio Canada".
Reading: News and magazines. I've been reading the "
http://journaldemontreal.com" website everyday, always with google translate ready.
Writing: Write small texts about your life or giving an opinion about an article you read.
Speaking: Find a recorder app and talk about an article you've read, giving your opinion. Sometimes create a "diary", narrating your daily activities.
For speaking and writing, it's vital to find someone to evaluate you, because it's hard to know exactly at what level you are.
Most important, take as many prep tests as possible, to get used to the types of questions from the exam. They always keep the same structure, just changing the situation and vocabulary.
You may find these 2 books online: "TEF Objectif Reussite" and "TEF-250".