You can definitely can get great smoky flavor using a gas grill!
What will be different is the type of foods you’ll be grilling on a gas grill versus on a smoker.
Smokers are intended to be used at very low temperatures (225-275oF) for long periods of time (anywhere from 3-18 hours).
Smoking for long periods of time requires a large amount of propane, and it can be difficult to get the temperature of a gas grill down that low.
The best way to approach smoking on a gas grill is to smoke quicker-grilling foods like ribs, chicken, or pork chops.