The answer to my dilemma was simple, I needed to choose the skill whose evolution would benefit my upcoming class the most. At the same time, I had to consider which skill I felt confident enough to evolve on my own.
For the first question, the answer was clear [Essence Manipulation].
Since I was aiming for an Essence-based class, evolving this skill would be the most beneficial.
As for the second, it had to be [Seismic Burst]. I was confident I could evolve it myself. Since it was an attack skill, I could study other offensive abilities and find a way to refine it further.
My mind drifted to Guro's last moments, the instant I used [Seismic Burst] and unintentionally created fire by manipulating heat particles and Essence.
If I wasn't mistaken, that was what had caught June off guard. As a Master Rank, she must have sensed me manipulating the heat energy around me.