he appreciates the value of something, rather than the intent. buy him a gift, with the mindset of wooing him? he’ll appreciate the present for what it’s worth, what use it has to him, rather than any sentimental aspect or the person that gave it to him. a debt would be created, of course, which he would feel inclined to return. tell him the positive effects of something he’s done, for you or for someone else — give him the emotional insight that he likely lacks. that has a good chance of showing a visible reaction.
as for his sense of humor, it’s a toss up between grim and slapstick. physical comedy gets him, such as a drunken mercenary slipping and tumbling down the stairs, or the juxtaposition of a qunari with a dwarf in their lap. his laughter is not meant to be malicious, but could be interpreted as cold.