Do we first develop gastritis on advil and then progress to ulcers? or can directly get ulcers on various sites of stomach lining without gastritis

All of the above: All NSAIDS ( Advil, Aleve, aspirin and generic equivalents) are ulcerogenic; howverver, many gastric and peptic ulcers are caused by the bacteria, H. pylori. Best to get tested if symtomatic. Excellent mediciations such as Prilosec ( omperazole) and Nexium. Zegeri are PPIs ( proton pump inhibitors) will suppress acid production.

Caution Heart , Live: Advil initially causes gastritis and develop erosions if continued, Advil may cause ulceration of the stomach or intestine, and the ulcers may bleed. Sometimes, ulceration can occur without abdominal pain; the only signs or symptoms of an ulcer may be black, tarry stools . Ibuprofen should be taken with meals to prevent stomach upset Caution re interactions and effect on liver. Heart

Gastritis: One can have gastric ulcer disease or peptic ulcer disease with or without the assistance of NSAIDs such as ibuprofen, naproxen or aspirin. It is best to take the smallest dose of NSAID for the shortest time needed. Take with food.