It's unlikely you are to gain decent profit from host events, unless you are lucky. I'm warning you right now that trying to squeeze your way into the deep trading aspect of the game will be difficult, BUT this is not always true. You just have to find the right people. You will have a hard time negotiating with top traders (or rich experts) unless you have in-demand rares.
I suggest:
-- Play as many minigames as you can. This includes Fireworks, Jungle Cruise, and the Shell Minigame.
-- Go into "free giveaway" rooms, and you may get a really good item!
-- Stock up on Silver Keys and Ornament Crates, and trade them away in bulk. (Or you can use them if you want, but I recommend you don't because you can only get gingerbread items)
-- Save your credits for magic pins. Magic is almost always in good demand when they are first released, so buy them quickly and trade them off. Make sure you buy 1* magic pins ONLY, because that is what people really want; not combined magic.