Depends on whether you are a total beginner or have studied it before. I studied French in secondary school up to A-level but that was 15 years ago. Since leaving school I took French classes on and off but nothing intense. I started studying French seriously around July 2019 and I believe my level then was around A2 (which is like an advanced beginner). I took my first TEF in September 2019 and got B1s which gave me 4 points. I took it again in Feb 2020 and got B2s but not high enough to give me the 42 point boost I was seeking. I'll be retaking the test next month.
Based on my experience, my recommended approach would be to take classes at your local Alliance Francaise (I did 8 hours a week of classes for like 3 months) and then when you get to A2 level you can supplement these with 1 on 1 tuition with a tutor who specialises in TEF. I know a great online tutor - feel free to message me and I'll share his details with you. Initially, I found that my reading and my writing were a lot better than my speaking and listening, but after my private tuition my speaking is now one of my strongest abilities. So, in my opinion, for speaking at least you will need to have 1 on 1 conversations with a tutor who can correct your pronunciation, syntaxe and grammar. For reading and listening, you could just buy books like Tendances or Totem for your level (e.g. A2 or B1 etc) and work through them to improve your vocabulary and grammar. For writing, I find that the more you read, the more you become familiar with French syntaxe and sentence structures, and obviously working on your grammar is important. So, to sum it up, for your speaking you will need 1 to 1 tuition and there's no way around it unless you know a native French speaker who can help you for free. For writing, you can do a lot of the work on your own (grammar, vocab etc) but ultimately, you will need someone to review your work and give pointers (especially for TEF as there is a certain structure you have to follow). For reading and listening, it's all down to you - it's entirely self-study. Best of luck!