The reader can be heplped to identify how rich Gatsby is first of all , by getting to know about the mansion he lived in.In chapter one Nick, the narrator mentions it..."a colossal affair by any standard.."on page 7.He goes on and mentions the house resembles.."some Hotel de Ville in Normandy.." because of a tower held , a majestic swimming pool and the 40 acres around the mansion.In chapter 2, page 36 when Nick goes to meet Tom´s lady in her appartment, some guest to the improvised party says that Gatsby was.."a nephew or cousin of Kaiser Wilhelms.." the leader of Germany during the Great War. Then , Gatsby had to be rich and powerful.Finally, in chapter 3 , Nick comments on the parties held at Gasby´s house and gives the reader the idea that thousands of dollars were spent in holding those parties.On page 43 he tells ..."on week -ends his Rolls Royce became an omnibus..".." At least once a fortnight a corps of caterers came down..."
With these images, and the use of diction it is very easy for the reader to figure out that Gatsby is immensely rich.