The allegory of the failed prospector
Twain describes his life in Nevada through the allegory of a failing prospector. In other words, Twain wants the reader to know that he wants to "strike gold" in some way. When he gets there, no one is holding him back in any way. He is eager to get started, makes friends quickly, and before long, there's a group of guys that are happy to have him. Twain shows us here that he is socially winsome and often garners the help of others, even the help of strangers. Then, when he fails, he doesn't stay away forever. He learns from that failure and reiterates in San Francisco, but to no avail. When he leaves the prospecting business, it's like him finally giving up on playing the lottery. He frees himself to see more opportunities than the ones that lead to quick wealth, and before long, he "strikes gold" in a different way.
The allegory of "striking gold" in Hawai'i
When Twain gives up on his misguided dream of striking gold, he realizes that if he were to get a job, he'd like to write if possible. Within no time, he's a reporter, living on the Sandwich Islands (now Hawai'i), and he realizes that his dreams for life have already come true. He has found bliss on the islands, writing about what their culture and nature are like. He has truly "struck gold," by finding his destiny and his bliss.
Accepting the call to adventure
Twain exits the narrative at the end of the book to speak directly to the audience. He tells us that young adults should leave their homes entirely. He says that by moving yourself to a new environment, and by struggling toward independence without the assistance of loved ones, that a person will discover who they really are in the world, and their perspective about what life really is will be broadened. That means that he views this novel as a kind of bildungsroman, and the continual attempts at life in the West would be Twains response to the "call to adventure."
The motif of paradise
Hawai'i is an island paradise unlike anything Twain could have imagined. And to be hired as a reporter in those islands is an even bigger treat, because he spends his days truly appreciating island life, island culture, the rich history and mythology of the island's native population, etc. Then, he writes about what he learns. This is paradise for Twain.
Paradise is what Twain was looking for when he moved to Nevada too though, and if he had found gold, he certainly would have called Nevada paradise. And when he moves back to San Francisco, what is he looking for? Technically, he's looking for gold, but if he found gold, certainly he would have called San Francisco paradise too. The point of the novel is that the entire world is beautiful and meaningful, and true "paradise" is to discover one's destiny through adventure.
The motif of struggle, failure, and grind
If Twain is on a hero's journey, then he will have to persevere through a long series of trials and tribulations, and that is definitely the case. He fails in Nevada (although not without successes of different kinds), and then he has to endure two boring years of office work back East. After that, it's back to the grind, and he tries pan-handling again. Finally, he accepts his defeat, but ironically, the journey has been successful in the ways that truly matter, and as a reward, he gains his reward: he will live on Hawai'i and be a writer.
