If you are confused whether you should buy leetcode premium or not.
Disclaimer: For people who are ready to consistently dedicate 4-5 months for preparation.
Tips
Before buying leetcode premium

1. Don't buy leetcode premium unless you have solved atleast top interview questions. (Idea:Having solution at your discretion limits on how much you put effort to reach till solution.
   Initial stage: Focus on reaching to the solution. And then try to decrease TTAS (time to arrive at solution) by average 10 min.
2. In the beginning, focus more on reaching to the idea and pseudo-code correctly. (Pro Tip: use pen paper/ docs to think on the idea). Attempt the code.
3. There are atleast 145 problems in that category. Target weekly atleast 15 problems(avg 2 problems/day) Discuss questions that you are not able to solve with people around you or checkout the discuss section.
4. Initially sort it difficulty level wise (This is the best way to avoid discouragement). Then cover topic wise.
5. Gradually, build up to get the code right. Check out others code and build/get inspired from standard templates (Like recursion(computing in head-recursion/tail-recursion), backtracking (when need to use by reference/by value argument), approach for memoisation, top-down vs bottom-up approach, etc).
6. Use leetcode creating list option (to-do attempt/to-do code /solved completely or by idea)
7. Solve daily questions from monthly challenges. This will help in building daily consistency.

Note V.V.I: Dont get discouraged, if from any particular topic you are not able to solve questions. Just note down than your areas of weekness (topic/difficulty).

After around 8-9 weeks of preparation the problem solving skill would be improved to a sufficient level. Now comes the stage of dedicated preparation.

1. Checkout dedicated topic-wise preparation list from explore section(depending on the weak areas).
2. And start with company wise list (e.g. google). Solve atleast all last 6 months questions.
3. Participate in the weekly contest. Try to reach to the level where able to solve atleast 3 questions in weekly contest. And all questions in biweekly contests. Biweekly are usually easier than weekly.
4. This should take total of 1-2 months of dedicated preparation.

P.S. This is what I feel from my experience. Please let me know in comments if any part does not make sense or you think otherwise.