This type of guild war is mainly designed for beginners, so they don't have to build any kind of PvP items for this. All what's needed is lv 35 chars or higher and the Arena items purchased from NPC Hong-Hae in map 1 of each kingdom. No other items can be used during the war, because the access won't be allowed in the battle map if they are equipped on the character. Inside players can use potions but they won't be able to use mounts.
As described in this post: FUTURE UPDATES players have to farm coins, buy the power ups and then overrun the enemy base. In the attachment of this post everyone can find the map with the objects of interest. I never had the chance to do a very good testing of the field but it's a very good map for large groups of players, regardless their lv and skills. Also I believe it needs a full set of Arena items, not just the weapon and the armour.
The map is huge, it is very good if each guild comes with 8 players or more. Who get's killed is teleported back to own base, which is very good for defenders but very bad for attackers. Power ups matters and once they are used they count for the whole guild for the duration of the war; without them it will be just a senseless massacre. Metins don't have much HP, there are metins and bosses for coins (marked on the map) and metins and a Mighty Ice Witch to speed up the war by damaging the enemy metins of the opposite guild. The guild who manages to take out both enemy metins wins the war.
If there are players who think themselves as good leaders and good strategists, this map is the cheapest and the fastest way to improve their skills. It only requires some time and a bunch of friends willing to work as a team. I can wish you guys to have fun trying the map