There is a lot to learn and it might take a relatively long time to do it. It is further complicated by a fact that there appear to be many different kinds of Spanish. As with English the Spanish language has different dialects and accents. The people in New York speak a lot differently from the people living in Georgia or Minnesota. However the basic structure is the same and the vocabulary is the same. The same is not necessarily true for Spanish.
These two things appear to actually be quite different. Sure the language is the same, most things are the same, but there are some words that are different and there is a verb conjugation that is used in Spain that is not used in parts of Latin America. This should not be a problem of course; kind of like the English language in England has words for things that are not used in the United States. However, if you use a word in the US that someone would use in England 9 times out of 10 people will know what you are talking about. The same might not true when you learn the Spanish language.
Many students of a language would buy a Spanish to English/English to Spanish dictionary. This is easy enough except for the fact that with occasionally used words from the dictionary people might have no idea what is being said. The Spanish dictionary should be used in Spain or with people from Spain. Of course this important piece of information is not printed on the dictionary.
So when you think of buying a dictionary remember that there are nuances and differences that might cause you problems. So before you buy a dictionary be sure it covers different dialects or just buy a dictionary that is printed in the country of your target language. Some expressions will then make more sense to people you interact with.