Blood echoes are divided into three clusters: Green, Blue and Red.
Green to blue: Five Green clusters give one blue.
Blue to Red: Five blue clusters give one red.
In this sense, if Surgit wants to go from Strength Rank1 to Rank2, he'd need to spend Green Echo Clusters.
Let's assume Surgit is at Rank 1 in Strength. He'd be a Waste of Skin (1)
In order to go from Waste of Skin (1) to Waste of Skin (2), he'd need to offer one Green Cluster to the doll in the dream.
To go from Waste of Skin (2) to Waste of Skin (3); he'd need to offer two clusters, and so on until he reaches level (5)
In order to jump from Rank 1 to Rank 2: Hunter, he'd need to spend a Blue Echo Cluster.
Five Green clusters would give him a Blue Cluster. He could also defeat a boss prior to the Blood Moon to receive a Blue Cluster, or defeat bosses in the Chalice Dungeons. Either way, Surgit would need at least one to jump from one Rank to the other.
Leveling up to level 5 of Rank 2 would follow the same process, but with Blue Clusters this time around.
In order to reach max level in each attribute, Surgit would need to use Red Clusters, which are equivalent to 5 Blue Clusters, or 25 Green Clusters.
To sum up:
Echoes are divided in three Clusters, each classified by a color: Green is the weakest, Blue in the middle, and Red being the highest.
Each Cluster is divided to five levels, which allow the hunter to upgrade their attributes according to the ranks and levels they already have.
I hope this guide was helpful. Lemme know in the comments if you have any questions.
And as always, thanks for reading.