Plugins

CombatLog - This is so people cannot log out during pvp and not die, if they log out while in pvp combat you die and drop all your items, this makes it so people cannot log out on 1hp and wait until the person goes away.
PlayerHeads - This would be a cool feature, for instance, if someone killed Celtic, they would get his head. players could then auction the head to the players in the server. This would mean the players would have a rank (kind of) and this would incourage people to try and get other people's heads to sell them.
ProtectionStones - You use ore to claim land e.g. coal ore 11x11 redstone 21x21 diamond ore 41x41 So people can claim there own land.
SilkSpawners - This is so people can mine spawners (Personally i think it would be cool if this was added, so people can build really cool farms without someone else coming along and taking your spawner.
Essentials - Kits/Ban Perms/ Tempban Perms/ all the things related to the essentials below.
EssentialsChat - There could be a tier donation which gives you a coloured name/nickname. This is optional.
EssentialsSpawn - with this, you can add /warps, so you can set up /warp wild, so every player can go out far to setup a base, the /warp wild would be different every time so people wouldn't be going to the same place.
GroupManager - This is so you can add trusted players like your mods/admins so if you're not on a trusted player/one of your mods in twitch can roll back someone's base.
Prism - This is a plugin where it allows you to roll back certain parts of the world. If someone comes on and greifs the server/someone house/farm you can roll it back with a few simple commands.
WorldEdit- this is optional to you, if you want it to help build the spawn ect.
WorldGuard - This is so you can guard certain parts of the world such as shops ect and also the spawn part, so when new people come on the server they won't instantly die.
Lockette - This is the plugin where you can throw a sign onto your chest and put [Private] You can add a few friends to the chest also so they can come into it, this stop's people stealing from your chest.