Trying to make everything of the show's underlying story arc about Jacob finding his replacement make sense, I came up with these ten points/mini-essays:
1. Jacob has been bringing people to the Island for millennia, trying to find someone who can take over his role and thus kill his brother.
2. Jacob's plans become increasingly philanthropic: he tries the US Army, then the Dharma Initiative, with his chosen candidate leading each group. They prove unworthy and so Jacob decides to go on a big recruitment drive. He brings together a group of people and ensures that they get on the same plane, recruiting from an early age those time travellers who he saw inciting the Incident. Knowing that a man who time travelled to 1977 left a diary describing the future in the care of one of Jacob's two chief lieutenants, he has his consigliere order the lieutenant in question to recruit the man described within the diary as electromagnetically resistant, so as to have a contingency plan should his brother succeed in escaping the Island, which would involve unleashing the electromagnetic energy caused by the Incident, which would in turn detonate the US Army H-bomb and obliterate the Island's underground supervolcano, causing a chain reaction which would rip apart the planet.
3. This achieved as of 2001, he finally begins in earnest to recruit the people he wants as his next candidates, choosing their numbers according to the principles of degrees in the circle surrounding the cave which contains the volcano's blocked entrance from which it is possible to enter the cave. It is at this point, having already been keeping an eye for decades on Kate Austen and James Ford, the two time-travelling ringleaders of the plot to contact his people in 1977 to incite the Incident, that Jacob travels to the mainland via the Tunisian wormhole to recruit Jin-soo Kwon and Sun-Hwa Kwon at their wedding (because they are dysfunctional people associated with Mr. Paik, an associate of former Other Charles Widmore), John Locke at the scene of his near-fatal accident (Richard having watched Locke since the 50s), and Jack Shephard at the beginning of his professional disillusionment. Jacob has been watching Sydney for potential candidates, i.e. dysfunctional lonely people, who could travel over the island, and has found Jack through watching Christian Shephard's frequent secret journeys to Sydney to see his estranged daughter. Having touched these six people with hands coated in water from the Island's volcano cave, he has ensured their immunity to suicide and to murder by fellow chosen ones while still dysfunctional. He uses his consigliere Richard to manipulate them towards boarding a plane in 2004. These are the six principal candidates, alongside which he recruits six others to serve as potential backups, and to be potential groups of eight and four, so as to match two of the degrees of possible cave entry.
4. These six others are Charlie Pace, Claire Littleton, Ana-Lucia Cortez, Eko Tunde, Frank Lapidus and Walt Lloyd. He recruits Charlie, Frank and Walt by continuing to watch for potential candidates in Sydney (Charlie through his brother, Frank through his job, Walt through his residence in Sydney). He recruits Eko, Ana and Claire because of their association with Yemi (see note 5), Christian and Christian respectively. Jacob is a hard, cruel and obsessed Knight Templar who does not care about the people whose lives he is endangering in his quest to manipulate these people into coming to the Island; he will eventually end up causing the deaths in the plane's crash of 265 innocent people, or about the risks he will be subjecting the 47 non-candidate survivors to. Frank Lapidus oversleeps on the morning he is due to fly the plane, due to a hangover, and as such Seth Norris flies the plane instead. He narrowly survives the crash by coincidence, but is immediately killed by Jacob's brother because Jacob's brother can tell that Norris has inadvertently brought people to the Island without Jacob's special permission, as Jacob had only given that to Lapidus. Jacob's brother is angry that more candidates have arrived, but pleased to find he can unexpectedly take it out on the courier.
5. Months before the crash, Jacob had brought a balloonist named Stephen Wallis to the island, giving him the cover identity Henry Gale, named after the balloonist from the Wizard of Oz. Jacob had hoped that Wallis could fulfil for the soon-to-be plane crash victims the same role fulfilled by Richard: to be a consigliere between Jacob and his chosen people (This was the same role intended in 2001 for Yemi, but Yemi died due to his abductors botching the job by falling foul of the military). However, Wallis attempted to shoot the Others when they came across his balloon, and they broke his neck and killed him in response, on Richard's orders, which Richard falsely claimed were Jacob's.
6. Jacob took the following methods to ensure that his chosen dozen boarded that plane: he befriended Christian Shephard and kept him a dysfunctional alcoholic, destroying his career and finding for him the address of Claire, his biological daughter, encouraging him to go to Sydney to confront her; he instructed Richard to bribe a Sydney confidence trickster into paying Claire to board the plane by convincing her to give her baby up to a fictional Los Angeles couple; he got Ana Lucia the job at the Sydney airport so she could meet Christian, by getting the previous occupant fired and then ensuring she saw the ad; he had his associate Matthew Abaddon persuade Locke to go on an Aboriginal walkabout; he set up the deal with associate Mr. Paik so that Jin and Sun would go to Australia on Jin's business; he contacted Hibbs and told him the whereabouts of Frank Duckett, and recommended Sawyer for assassin; he got Susan Lloyd the lawyer job in Australia and gave her her fatal blood disorder; he had alerted Hibbs to Sawyer's existence and potential as an employee in the first place; he arranged the romance between Liam Pace and an Australian woman named Karen; he faciliated Liam's rehab and move to Australia; he set up Charlie Pace's potential deal for a series of reunion gigs so Charlie would visit Liam; he got Eko Tunde the priest job in Australia; he arranged the romance between Diane Austen and Wayne Janssen, facilitating Kate's parents' divorce, and encouraged Janssen's existing abusive tendencies; he leaked the information to Kate that Janssen was her biological father; he ensured that Kate saw attractive brochures about Australia and arranged for her to receive false papers helping her to escape America.
7. Once these twelve people and a host of others had arrived on the Island, Jacob issued instructions to the Others to kidnap Austen and Ford, his two longest-term groomees, so as to persuade them to serve in the consigliere role intended for Wallis. The Others, however, led by Ben Linus who, like all of the Others save Richard, had had no contact with Jacob and regarded him as semi-legendary, decided instead to prioritise the solving of their fertility problems, caused by the Island's high levels of post-Incident electromagnetic energy, and so did not get around to following Jacob's orders until near the end of Season 1, at which point they decided also to kidnap Walt, the youngest and most Island-attuned candidate; then in mid-Season 2 Ben Linus decided to approach Jack Shephard to persuade him to perform surgery on Ben's tumor, deducing that he could try to recruit Locke at the same time; however, this failed when he was captured. Walt's psychic connection to the Island and his resistance to the Others' heavy-handed approach, combined with his newfound unexpected attachment to his father, caused the Others to abandon Walt's potential as a candidate and instead focus on the recruitment of Austen, Shephard and Ford.
8. The Man in Black had begun a concerted campaign to lead the candidates to their deaths, appearing for that purpose to Jack in White Rabbit, Sawyer in Outlaws, Kate in What Kate Did, Eko in the 23rd Psalm, Charlie in Fire + Water, and Ana-Lucia in Abandoned, plus Locke in Walkabout and Exodus. The Man in Black also attempted to lead Hurley Reyes to his death after identifying him as a positive influence on the group; by appearing to him in Dave. By early Season 3, Walt was out of the picture and Ana-Lucia and Eko were dead, both the latter two because they had resolved their emotional issues and thus ended their potential candidacy in Jacob's eyes, meaning they could be killed. Had Michael shot Ana half an hour earlier, before she dropped the gun on Ben, she would have survived the bullet.
9. Having heard the Others discussing the imminent freighter arrival, the Man in Black decided he would attempt to help the candidates to leave the Island; his plan was to persuade all nine of the remaining candidates to board the ship; he appeared to the trustworthy Hurley Reyes and the gullible John Locke, and told Locke to move the Island, hoping that with all the candidates gone, the Island would not travel through time as it was bound to do should any candidates remain on it during its moving; for that would cause the Island to jump around between times of great change on the Island, until someone else returned the wheel to its stable position. The Man in Black decided to retain one candidate whom he could use to disable the volcano so he could escape, so he kidnapped Claire. He had hoped that with Claire corrupted, Locke transported to Tunisia, and Jin, Sun, Kate, Sawyer, Jack and Lapidus off the Island, he would have a safe environment in which to use Claire to leave the Island.
10. That plan failed when Sawyer stayed on the Island, so he hatched a new plan: get them all back and kill them, then again use Claire to escape. Once the Oceanic Six had left the Island, only Sawyer and Jin remained on the Island as candidates. With Claire corrupted, Jacob sought to bring the number of candidates back up to six by persuading Jack and Sun to return and replacing the dead Locke and the emotionally healed Kate with Sayid and Hurley. He had Widmore arrange Nadia's murder, hoping to persuade Sayid back to the Island, but Ben hijacked that by recruiting Sayid as an assassin. It was at this point that Jacob decided to focus on Hurley by sending him visions of those who had died on the island and whose spirits were thus preserved on it while their bodies remained unburnt. This tactic eventually worked.