How do the past events in Scrooge's life influence his personality in Stave 1?
In his past we know four main things: he was sent to boarding school and was very lonely; he had a sister whom he loved dearly, but who died young; he worked as an apprentice at Fezziwig's lending house; he was engaged to and then dumped by Belle when she decided he was too greedy.
His time in boarding school perhaps prepared him to be lonely later in life. His greed and selfishness have pushed people away and although he realizes the distance they keep, he actually likes it. He is not a social man, or at least he hasn't been in a long time.
Scrooge was close to his sister, but we know he was not close to his father and we never hear of his mother. Therefore we get the impression that once Fan died, he had no one else that he really cared about. Once again, he felt alone. Her death may have influenced him to shut off part of the world, as he may have felt no reason to be connected to it.
His work at Fezziwig's influenced him as a successful businessman, but it did not actually influence him to be a better person, like it could have. Fezziwig was a very good employer and man, and Scrooge is neither. So, sadly he did not learn anything personally valuable from Fezziwig.
Although he did become engaged to Belle, it was when he was poor and once he grew successful and wealthy, he showed her no love or care. This represents how he treats all people in his life, and it shows that his love for money influenced the way he bag to treat others.