To upgrade your Hearthcore ruin, you need Hearthcore Shards.
With each upgrade, you need more Hearthcore Shards.
Below is a list of possible ways to gain these.
Gems
You can purchase Hearthcore Shards using gems.
1 Hearthcore Shard = 15 Gems
10 Hearthcore Shards = 125 Gems
100 Hearthcore Shards = 1,154 Gems
1000 Hearthcore Shards = 10,000 Gems
Chest
You can purchase a chest using guild coins to have a chance at
gaining extra Hearthcore 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 Hearthcore shards.
Elite 3-1
Elite 3-2
Elite 3-3
Elite 3-4
Elite 3-5
Elite 3-6
Chests
Chest from the VIP daily clan gifts (Flamehammer city) gives Hearthcore shards too.
VIP Daily Clan Gifts
You can collect 3 Hearthcore shards per gift from daily VIP Clan gifts (Once you have level 25 diplomacy for this city).