Got many ways to upgrading your wall..
Normally People will..
Level 1 - Carnelian Wall
Level 2 - Topaz Wall [1000 Lumber]
Level 3 - Amethyst Wall [2000 Lumber]
Level 4 - Sapphire Wall [4000 Lumber]
Level 5 - Emerald Wall [8000 Lumber]
* That the basic upgrading and must...
Now.. Depend on how pro vampire are...
If vampire pro or not..
I suggest upgrade to
Level 6 - Chrysoprase Wall [30 Gold & 16000 Lumber]
For beware only..
Then Destroy your Level 6 - Chrysoprase Wall and
use your Blood Elf Builder to build level 9 - Ruby Wall [250 Gold & 128000 Lumber]
Or if you think you're safe.. Just farm and then use Goblin Tower Builder to build Level 10 - Diamond Wall [440 Gold & 150000 Lumber]
If Pro
I think You must directly upgrade
Or you can tank with Level 7 - Garnet Wall or Level 8 Platinum Wall inc. Wall Plating (That depend how how pro vampire are , Upgrade like this will cause more resources than just build a ruby wall instead )
Direct Destroy And build Diamond Wall if you got $$..