Hey!
I wouldn't say that grammar is not important at all. For B2 you shouldn't make basic grammatical errors and typos like accent in "métro" for example. Your spelling needs to be correct for all simple-ish words. Unfortunately, unlike for English, for French there isn't a dictionary available publicly with a level marking for each word, but for B2 you should not make any errors in words that are A1, A2 and B1 level. Plus, make sure you master COD and COI, use verbs with the prepositions correctly. These are the heart of the French language. Nous and adjectives need to be correct and agree by gender.
As for tenses, you should conjugate/use correctly in any person, plural or singular with no errors:
- présent de l'indicatif
- pariticipe présent (not a separate tense, but still important)
- future proche / futur simple
- passé composé / l'imparfait (and use these two appropriately, not confusing them)
Can use 1 or two times just to demonstrate your level, but do not make mistakes in these:
- passé récent
- présent continu
- subjonctif présent
- plus-que-parfait
- conditionnel présent
Vocabulary you can pick up when you listen/read to authentic content like youtube, news, etc. Check out TV5Monde website, they have a lot of that and sample TCF tests to familiarise yourself with the format and topics for which you need to pick up the vocab.
With your level it's best to take classes with a tutor who knows the exam format and prepares specifically for TCF. Alternatively, check out youtube, there are videos with written task 1, 2 and 3 as well as oral.
