Charlotte, daughter of Sir Lucas, represents the upper class of knights, who have the lowest rank of nobility as the title is not hereditary: it does not pass on to a son. Sir Lucas demonstrates upward class mobility since he was beknighted by the Queen and thus entered the the knighthood. Mr. Collins, whom Charlotte marries, represents the working class comprised of lesser clergymen, doctors, teachers, merchants, and such. Charlotte is in a higher class than Collins due to her father's knighthood. When Collins marries Charlotte, he rises in social class by virtue of his connection to her family.
Wickham represents the same class as Collins’ because his father was employed as an estate steward. While he is in the regiment, he is in the army and navy officer class of men (restricted to men then). Members of his lower class, who had neither social position nor income to buy themselves a commission but who had a benefactor who would buy a commission for them (as Darcy bought Wickham's commission), could rise in social class because of the connections he would make with the sons of nobility and independently wealthy gentlemen; these almost exclusively made up the membership of the army and navy officer class. Wickham thus rose in social class while in the regiment. He rose further, after being forced to marry Lydia, through the connection of marriage to her father, because Mr. Bennet is an independently wealthy (though running out of money) country gentleman. Wickham’s character illustrates two ways to rise in social class. Had he accepted Darcy Sr.'s provision for the clergy, he would have illustrated a third way the lower class might rise through a financial benefactor.
The Bingley's represent another way to rise in social class. Their father is a manufacturer. He started out as a tradesman in the same class as Collins and Wickham. He made a great success in his trade. He accumulated wealth and through wealth alone rose to the level of independently wealthy gentleman. However, he was not a country gentleman as Mr. Bennet was. He, Bingley's and Caroline's father, was a gentleman tradesman. The Bingley's rose in social class through success and the acquisition of great sums of money. The family rose so high through money, in fact, that Bingley was seen as a fit companion for the independently wealthy and aristocratic Mr. Darcy.
Jane and Bingley didn't really change their classes when they married because they were both of the high class of independently wealthy individuals. However, Jane did secure her position in their class through Bingley's wealth, and Bingley did enhance his stature in their class because of his connection to the country gentleman, a connection which overshadowed and improved the tradesman root of his wealth.
Though Elizabeth and Darcy are in the same class--Bennet and Darcy are both independently wealthy country gentlemen. Darcy however has connections to the highest class through his connections to Lady Catherine de Bourgh and his cousin Colonel Fitzwilliam, the son of an earl. Elizabeth, like Jane, secures her position through Darcy’s wealth but also rises to the highest class because of her connections through marriage to Darcy’s hereditary nobility. (This class distinction indicates why Colonel Fitzwilliam chooses to be highly selective about whom he marries: if he wants to retain his status in the highest class of nobility, he must marry a woman in that class.)