Welcome!
I took the course 2 years ago, class #4, and if you look through my previous post, I've given my personal thoughts on the ITC course.
In a nutshell, if you are working with client that require Absolute temperature measurement, then take the Level 1 sUAS course. Just be well prepared for the information.
If you are doing simple Qualitative measurements, then pick yourself up an affordable handheld and start taking data, and start to analyze and understand what you are seeing.
Going to FLIR's DELTA series is a good start.
Oh and yes having a handheld , as opposed to flying or hauling your aircraft around everyday to capture data is a lot easier.
Having practical experienced has more weight than having a certification. I was a self-taught drone thermographer for nearly 3 years before ITC offered their sUAS course.
I will not stop anyone from taking the course, but if the cost-to-knowledge transfer is not there, then it is money wasted.
What I mean by that is thermography, like any acquired skill, needs constant exploring and learning.
This is my latest testing aka "screwing" around to see the performance of my 3D printer's hot bed on my FLIR ONE Pro.
*Just because one is certified, it doesn't meant they are proficient at their skill.