He's arrogant, abrasive and agressive, though in "actual life" generally keeps up a more agreeable fašade. His low opinion of amateur writers stems from the fact that he makes something like a living writing - formulaic pulp fiction, but since he's getting paid for it he's obviously better than us.
Gabriel is 1,85m/6'1" tall, on the strong side of athletic, has black, shortish hair, blue eyes and is quite fair skinned, but not unusually pale.
He needs fresh blood to stay alive. Sunlight is deadly. Holy symbols by themselves are no problem. Garlic's good, though you can have too much of it, but artificial and/or sweet scents, particularly vanilla, are sickening. Entering a home or sanctuary may be only possible only after being invited. Crossing a stream or river is draining.