This may seem like common sense, and I'm sure it's been stated many times in the dozens of existing threads about money problems, but I don't know how else to put it. Your amount of in-game silver/gold depends 100% on what you do in-game.

If mostly you do the quests that don't involve much killing and that don't have high payouts, you will have less money.

If you spend a lot and don't do things to recoup that money, you will have less money.

If you group more than solo, you will have less money.

If you focus more on the quests that do have good payouts and that involve killing mobs, and you then sell the loot, you'll have more money.

If you sell a lot without spending a lot, you will have more money.

If you solo more than group, you will have more money.

You can take two different people with the same class and race but different play styles, start them at level 1 at the same time, and compare money at level 35 and find very different results. One might have 10 gold while the other might have less than 100 silver.

It's all about what you do in-game to either get money or lose it.