Well, italki is a marketplace to connect teachers and students, so it can obviously be of great help. Whether you end up improving your skills or not is a different story and depends on many different aspects, starting with how much effort you are willing to put into your own learning process, how clear your objectives are, what your current level is, choosing the right teacher for you, etc., etc., etc.

Is your question is "are the teachers good?" My answer is, "yes." I have paid money for lessons in Spanish from two "professional teachers" and two "community tutors." I have thought all of them were excellent and worth the money. Because of the way italki is set up, the risk is small. Most teachers offer inexpensive trial lessons, and let you book one lesson at a time. Suppose you just don't like a teacher, but teacher isn't doing anything wrong, so you can't really complain or hold back payment. You've only wasted about $20, not about $250 to buy a course like Rosetta Stone or Pimsleur. Automated tools like Duolingo are valuable, but there is no substitute for live lessons. Yes, it is annoying that you need to begin by buying italki credits and you have to buy them in multiples of $10. It is difficult to buy the exact number you need, or end up with exactly $0 in your account after the last lesson. (I don't think) you can get back unused credits. If you are living in India and are planning to learn English for use in India you might want to take that into account when looking for a teacher.

I don't think so . because this issue depend on you not on italki .