When held in the offhand, Focus items can add to your maximum amount of available mana. Some will have no requirements attached to using them, but will usually only yield a few extra (3, as an example.) More powerful versions will have a requirement, for example, +10 Energy, Fire Magic 7+; in this case you would need to have your Fire Magic attribute at level 7 or greater to gain the full benefit of the focus.Guild Wars 2 As you can imagine this is only beneficial if you have a focus that applies to a magic line that your character uses. One is available for each casting-related attribute, as such, it is very common to see mage type characters weilding these. However, melee types that use high energy attacks can be seen making use of them as well, for example, Warrior/Elementalists. However, a focus adds no innate defense bonus (though defense bonus modifiers can spawn on them.)
Shields help increase your character ability to defend themselves, and come in one of two basic varieties: Strength shields, and Tactics shields. Between the two, Tactics based shields are much more common. Like focus items, shields will often come with a requirement that must be met in order for your character to receive the full benefit of using the item. As an example, Tactics 9+. Because of this, Strength shields are only useful to a primary Warrior (as no other characters have access to the Strength attribute) and shields in general only useful to Warrior primary or secondaries that plan in speccing points into the Tactics line about cheap Guild Wars 2 Gold.
So that is all fine and well for the close range stuff, but what if you want to use bows, you say? Well, we can cover that, too. Bows are two handed weapons, so you will not be able to equip anything in the offhand.Guild Wars 2 Gold Bows also have a varity of different ranges - some are long range, but slow attacking (Longbow, Flatbow, etc.) while others have a short range, but a faster attack speed (Shortbow, Hornbow, etc.) It is usually a good idea to bring one for each base type (long or short range) if you must choose between them, then let us buy Guild Wars 2 Gold.