IGCSE solely means International GCSE - It isn't an exam board.
There are several IGCSE exam boards - CIE (Cambridge) is the most common one but there are IGCSE for Edexcel as well (I think there is one for AQA).
If you mean CIE - I sat it last May. I got an A without any preparation and as a second language speaker.
My tip is that you should do past papers. CIE IGCSE English language is ALWAYS in the same format - 1st question is a heavy writing question which requires you to write a diary, letter, report etc. 2nd question is always "writing effect" which doesn't require a good grammar or any other writing skills, but makes you think. 3rd question is always 2 summary question.
You will gain most out of past papers seriously.
Remember though, the coursework essays (3) are a big chunk of the final grade. So be creative, use thesaurus, and don't leave until last minute (I left it last minute and done it over 2 nights or something lol it was a huge stress)