So, I would preface any advice with being clear on what your goals are and what you mean exactly by "learn Spanish." Do you mean get by conversationally? Are you looking for fluency certification? Do you want to attend a Spanish-speaking university or work in a Spanish-speaking office? Do you need to read and write Spanish, or just speak it? All of these things will have different needs, different vocabulary, and different methods.

My advice here is mainly for learning conversational Spanish.

Work one-on-one with a language tutor. For vocabulary practice, use a spaced-repetition system like Fluent Forever (I think Memrise has the same system).

But the biggest thing you can do to learn - speak the language. That's the most important part.