It is quite hard to advise someone on choosing a target language to study. There are many factors to take into account, the main one being the person's personality and taste.
Some questions that need to be answered Edit
1. Why do you want to study a language in the first place? Is it just for practical purposes like travel to the country where the language is spoken or communicating with family and friends over there? Or is it about preserving the mother tongue of your ancestors?
2. What is your prior experience with studying languages? It is a truth universally well known that the more languages you already know and the more experience you have, the easier learning another language gets. If you're a beginner to language learning in general it might be wise to consider languages from the same language family as your native one. However, while learning an "exotic" language (and by that I mean a language not popular in your homeland and very different from your native one) might be more difficult, you might find that it is more rewarding for you.
3. What materials are available for you in your country? It may turn out that it is quite difficult to find some and that isn't a good motivation. "Materials" could include text books and courses but also native speakers and books or movies originally made in the target language.
4. How interested are you in the culture? Most people claim it is a very important factor in terms of motivation. Maybe you have a favorite writer whose books you want to read in original version or a director whose movies you want to watch without subtitles or dubbing, or a favorite song which you want to understand? These types of reasons and methods will make your study more fun and interesting.