1916. Exams of English
I would say to candidates and examinees of First Certificate, of Cambridge University, that they should take the exam when they have high communicative competences and potentials.
As well, before the exam proper something useful and helpful is to read texts in English: they prepare you for the aural part and the rest of the parts too.
Take into account that First Certificate means that you’re capable to utilize the language in various contexts, about varied topics, with the ability of expressing what you think.
The equivalent is B2, within the European Common Framework.