What level of English proficiency should I have?

Level A of the Cambridge First Certificate in English (FCE) and above,

or a score of 550 on the paper based, 215 on the computer-based, or 90 on the Internet-based TOEFL (Test of English as a Foreign Language)

or an overall band of 6,5 on an IELTS (International English Language Testing System) test, with no individual score below 6.