This question, or a variation of it, seems to be one of the most common things asked on language forums and groups by aspiring polyglots. The problem with this question is that the person asking it is truly the only person in position to answer this. From personal experience, if your heart is not entirely into learning a specific language, you will not get far in your language learning journey.
Also, some people who choose to study a rare language may find themselves constantly feeling they have to explain to others why they are learning it. You should not have to justify your choice to learn a language, regardless of how ‘unpractical’ others may find it. For many of us, language learning is a hobby like many others. For example, there are many people who like to spend time learning to play an instrument. However, the chances of making a living with their music skills is slim. Yet, such people are rarely bombarded with discouraging questions and statements such as “Why?”, “You’ll never use it.”, or my ‘favorite’ – “Why don’t you learn something more practical?”
The fact is that you should learn a language because it makes you happy. You should feel free to learn whatever your heart desires. If you find yourself really wanting to learn a language with, for example, less than 100,000 speakers, then don’t hesitate to learn it ;). Even if resources are scarce, take whatever language learning materials you can find and start learning right away.
Polyglot in Progress 