What are the wealthy most afraid of? Of course, they fear death the most.
Poor people are afraid of death too, but the wealthy are definitely more so. That's the difference between dying without money and dying with a lot of it left behind.
Shava is in the process of transforming from a poor person into a wealthy one. However, his money didn't come from legitimate means. His rise has been quick, but it might get him killed any day, and such things are not uncommon.
Given Shava's situation, Gao Yang decided to gift him a bulletproof suit. As a boss, you can't always be wearing a bulletproof vest, especially when negotiating or meeting with another boss. Wearing a bulky vest would be embarrassing.
A suit that can save your life and looks stylish, and crucially is valuable, is something Shava could wear proudly for years.