ROK Gem Spending in Rise of Kingdoms

Focus all your Gem Spending on leveling up your VIP. Your first goal is VIP 6.

VIP level 7 at the start to give u alot of good boosts and the second builder form VIP 6
Focus reaching VIP level 10 to start obtaining the gold sculptures.
Use bare minimum to unlock Richard and Ysg from the Wheel of Fortune.
Focus VIP level 12 to obtain 2 gold sculpture
Work your way towards VIP 14 and if you are close to tier 5 unit then castle books (book of covenant) is a good place to use it as well.
After VIP 14, gems can be used to obtain Equipment Blueprint/material or Commander Sculptures