With regular deliberate practice, you can expect to be playing simple pop tunes within around 3 months. Within 6 to 12 months, your technique will improve and you will probably be able to work on bending notes (a very important skill for getting the best out of a harmonica).

So, you're a beginner and want to know which type of harmonica to buy? The short answer: buy a 10-hole diatonic harmonica in the key of C. Why? Because, most beginner lessons, and all of the lessons that I teach on YouTube and in my Beginner to Boss course are on the 10-hole diatonic harmonica, in the key of C.

Yes, but you can speed up the process a lot by learning from others. There are many great harmonica tutorials on youtube, for example. Different teachers work on different styles of playing and different genres of music, but the most common is blues harmonica.