To upgrade your The Guardian ruin, you need Guardian Shards.
With each upgrade, you need more Guardian Shards.
Below is a list of possible ways to gain these.
Gems
You can purchase Guardian Shards using gems.
1 Guardian Shard = 15 Gems
10 Guardian Shards = 125 Gems
100 Guardian Shards = 1,154 Gems
1000 Guardian Shards = 10,000 Gems
Chest
You can purchase a chest using guild coins to have a chance at
gaining extra Guardian Shards.
To purchase, click bag, click chests, click the third icon on right hand side.
The chest is called Magical Shard Box and costs 22,500 Guild Coins.
It randomly gives you 10 shards for any of the ruins or statues.
Campaign Elite Sweeps
You can sweet elite campaigns to pick up extra Guardian shards.
Elite 5-1
Elite 5-2
Elite 5-3
Elite 5-4
Elite 5-5
Elite 5-6
Chests
Chest from the VIP daily clan gifts (Anthropos city) gives Guardian shards too.
VIP Daily Clan Gifts
You can collect 3 Guardian shards per gift from daily VIP Clan gifts (Once you have level 25 diplomacy for this city).