In "Dusk," by Saki, the narrator shares the main character's disposition. The reader understands what Gortsby is thinking:
So Gortsby's imagination pictured things as he sat on his bench in the almost deserted walk.
Gortsby believed the defeated came out at dusk. He is feeling defeated at the moment:
He was in the mood to count himself among the defeated.
If the defeated show up at dusk, why is Gortsby out at this time of the evening? While some people who come out at dusk have money problems, this is not the case with Gortsby. He did not have financial issues:
Money troubles did not press on him; had he so wished he could have strolled into the thoroughfares of light and noise, and taken his place among the jostling ranks of those who enjoyed prosperity or struggled for it.
In this passage, jostling means to push or shove or to brush shoulders or elbows. Gortsby can fit in with the wealthy who brush elbows in upper class events. The jostling ranks would be the upper class people who enjoy money, those who rub elbows because of their prosperity. The jostling ranks consist of people who attend upper class events because they are wealthy. The jostling ranks have money through inheritance or through a struggle of hard work.
Gortsby is thinking that he can push and shove with the best of those who have money. He can brush shoulders or elbows with those who enjoy money or struggle for money. In other words, money is not the issue. Gortsby can hold his own when it comes to financial situations. Gortsby has money.
Gortsby is sitting on the park bench for another reason. He is preoccupied with something, but it is not a money issue. He can take his place with those who rub elbows in high ranked positions of society.
The term "jostling" was probably an accurate description of many of London's streets. Saki was born in 1870, long before automobiles were even thought of. Many streets in big cities were not even paved. This was what old timers used to call "The Horse-and-Buggy Era." The streets were filled with horse-drawn vehicles, including lots of wagons and also carriages, stage coaches, and various kinds of horse-drawn cabs. The sidewalks were extremely narrow, so there would inevitably be a lot of "jostling" on the major thoroughfares. Both men and women were high-top shoes because there was so much mud and horse manure. Naturally pedestrians would want to stay as far from the street and as close to the walls as possible, so there would be all kinds of jostling for space. No doubt people of Saki's time took all this for granted, just as they did with chamber pots and all sorts of other primitive facilities. Women were probably treated with some courtesy by the men on the sidewalks--but women did not venture outside their homes any more than necessary, especially after dark. There must have been a lot of "jostling" among the horse-drawn vehicles in the streets too, and crossing the dirty streets must have been a risky business for pedestrians. When the first automobiles appeared, they created more problems than solutions. They were noisy, not easy to steer, and they spooked the horses.