Pang here, just wanted to give you some friendly Advice. Did you know that you can click on the "Heading" or "Name" to bring you to a page that has more information? Go ahead and try. Pang Out.
Blue Elementor sets can only be obtained by killing monsters and in player shops. They are rare sets but have no bonuses. They will have higer defensive bonuses than normal sets. They are called Blue Sets because of the color of the name when you see the item in Player shops.
Rare sets can be dropped from monsters. They can also be found in player shops. However they are extremely expensive in most cases. Rare sets will give bonuses if 2 or more pieces are worn at the same time.