The biggest piece of advice I would give is to
have fun with it. Cubby and I have seen some genuinely scary pin traders at Disney who are kind of aggressive and show-offy and not very friendly, and there doesn't seem to be much childlike wonder or fun in their attitude (or Disney niceness, for that matter). We love pins and trading them but we like to have certain ones which appeal to us rather than whether they are rare or "worth" anything financially, and I think that's kept us with a healthier attitude about the whole thing.
David