Spanish is the official language in more than 20 countries, mainly in South and Latin America (in addition to Spain itself, of course). It is one of the languages with the highest number of native speakers worldwide – a numerous Spanish-speaking community, spanning Europe, the Americas, Africa, and some other places on the other continents.
Latin and South America are the major places where different dialects of Spanish and Portuguese are spoken. There are compact groups of Spanish speakers in the United States, too. Spanish-speaking communities can be found in more than 100 countries. This is why Spanish is so popular as a foreign language and it makes sense to learn it.
There are several factors to consider when choosing the Spanish language class to attend. First, similarly to English and the other languages spoken in many counties across several continents, there isn't a single version of Spanish spoken everywhere. The version of Spanish spoken in Spain (which is actually called Castilian, or castellano, not Spanish) is very different from the dialects spoken in Mexico, Argentina, Cuba, or the other countries in the Americas where Spanish is the official language.
Of course, the basics of Spanish are the same in all the dialects and if you're a beginner, then the difference is not crucial. Still, all equal, it is best to select a system, which is not focused on one dialect only because this gives you a broader idea about the language.
Another factor to consider when choosing an online Spanish class is why you need to learn Spanish. If you want to learn Spanish because you plan a vacation in a Spanish-speaking country, then you need conversational Spanish. If you plan to study or work in a Spanish-speaking country, than conversational Spanish alone won't help you much – you need a more in-depth course with lots of grammar exercises and writing activities.
If you have never studied Spanish, then an online Spanish course for beginners is your best bet. You can take a course with native speakers to improve your pronunciation and this won't cost you a fortune. Even private Spanish lessons are cheaper online, so if you need them, they are quite affordable.
Once you start the course, the most important thing is to be serious and to do your homework regularly. Spanish might be relatively easy to learn but if you're not diligent, this won't help you. Online Spanish classes make it so much easier to learn Spanish but still there is a lot you need to do, if you want to go beyond the basics.