Quizlet will save you! I got an A over summer (still have no idea how as I got a D in listening oops but I had two A*s and an A for the other sections) and it's down to quizlet and duolingo! Look up on quizlet your exam board e.g. "Aqa French gcse vocab" and you'll find all of the vocab on there (hopefully in different folders for each topic). I'm not sure if the new spec has different vocab but I know all of the old spec vocab is on there and someone made folders with it all in. You can do different activities with the vocab which is helpful. Also watch French TV/films/YouTube videos and listen to French music. Also get revision guides and workbooks as they can help a lot too! They'll probably been worksheets online to help with grammar and tenses and I reckon they're probably online lessons on like YouTube or something. Focus on your weakness e.g. For me it was listening so I focused more on that. Even if you don't get what you need for the test to be entered into higher, I'm sure they'll let you change if you push yourself as we didn't know until like idk March/April what we would be entered in for definitely.
Good luck! If it stresses you out or is boring, don't get discouraged as even though I got so worked up over it, looking back I weirdly enjoyed it all!