[wrholt]

Based on estimates that I have seen from a variety of sources and my own (non-scientific) observations while working for an ESL program for several years, many people can achieve an intermediate to intermediate-advanced level in a second lanague with around 1000 hours of dedicated study and practice, although a few individuals may need less time while other many individuals may need significantly more time. The length of time may also be influenced by the particular combination of first and second languages: it can be faster and easier to learn a language that is closely related to one you already know, and slower and harder to learn a language that is very different.

As for where to start: one cannot learn grammar without learning some phrases and sentences, and one cannot learn phrases and sentences without learning individual words or expressions. However, learning long lists of individual words or expressions without also learning phrases and sentences or grammar is useless: one cannot communicate merely by translating words one-by-one from English to Spanish.

Many people start by learning a few basic phrases or a typical short conversation that one would have on meeting someone for the first time, and use those as a basis to learn a couple of grammar points and practice them while also learning the individual words or expressions. Then learn another set of phrases, dialog, or text that include new words and highlight a couple of different grammar points to practice. Repeat a few hundred times. Mix it up to practice listening, speaking, reading and writing.