How long until I'm interview ready?

It depends entirely on where you are starting from, so the useful thing to fix on is a skill target rather than a time target. The bar to aim at is this: you are ready for most FAANG-style data structures and algorithms rounds when level 5 to 6 problems, which is roughly Codeforces 1600 to 1800 or a standard LeetCode hard, feel routine to you on problems you have never seen, and you can implement them cleanly under time and without bugs. Once you hit that, stop grinding algorithms and redirect the saved time into system design, real projects, communication, and the domain you actually want, because most people massively over-invest in raw problem count and badly under-invest in everything else that actually gets them hired.