Practical Marshallese by Peter Rudiak-Gould introduces Marshallese to the beginner. It is organized into 102 two-page lessons, each with a main grammar point and a vocabulary section. There are also Marshallese dialogues, general tips, and pronunciation practice in many of the lessons. Each lesson is designed to be a manageable chunk of new material that could be learned in one sitting.
The book is organized in order of usefulness, with the early lessons being crucial for speaking Marshallese and the later ones merely helping you express yourself better. Since the most useful lessons are at the beginning, you can go through as many as you like, stopping when you feel that your level of Marshallese is adequate to your needs. For instance, if you go through the first 25 lessons, you will know basic Marshallese grammar and about 250 words, which is enough to get by in many situations. If you go through the first 50 lessons, then you will know more grammar and about 500 words, which is enough to have decent conversations. If you go through all 102 lessons, then you will know all of the useful grammar of the language and about 1500 words, which is enough to have intelligent conversations on a wide variety of topics.
The lessons are organized sequentially, with each lesson building on the previous ones. For this reason you should go through the book in order, especially in the earlier lessons. It is not essential to completely master each word or construction before moving on, but you should at least be able to understand it when it comes up in conversation. Even if you can’t produce it yourself, if you can recognize it in conversation then it will quickly become part of your working knowledge of the language.
Practical Marshallese also contains a glossary of about 1500 Marshallese words and their English definitions listed in order of usefulness. It gathers in one place all of the words introduced in the lessons. This glossary is not intended to be used for looking up words either in Marshallese or English; for that purpose, you should use the Marshallese-English Dictionary by Abo, Bender, Capelle, and deBrum, since it is extremely thorough and lists words alphabetically in both Marshallese and English. But for building your vocabulary, the glossary at the end of Practical Marshallese is best because it lists only common and useful words, with the most useful words at the beginning and less useful words at the end.
There are also a small number of books published in Marshallese, and some published bilingually in Marshallese and English. These are mostly elementary school books with Marshallese legends and other stories. Although the Marshallese tends to be very advanced, these books are useful learning resources, and it would be worthwhile to get access to them.
Of course, the best way of all to learn Marshallese is to jump in and speak it with native speakers, no matter how little of the language you know. Practical Marshallese is only a supplement to that much more important resource.