The first year or two that I started developing B&W film, I've been trying all sorts of film, and would pick a developer just based on what seemed to be appropriate. Rodinal for Efke, HC-110 for tri-x, and then I would always have a "flavor of the month" tryout, like Rodinal Special on APX, etc. I eventually figured out that I wasn't learning much because I didn't compare things properly.
So after reading the Film Developing Cookbook, I decided to stick to tri-x and XTOL 1+1 in 35mm for a good time. I wanted to use tri-x because it had the look I wanted, and the Cookbook recommendation for 35mm was a developer like D-76 or XTOL. Being the edgy man I am, I went for the more modern product. Heh.
I would always try stuff on the side, but my efforts at finding a proper dev time were geared towards that combo. And I stopped using other formats as well for a bit.
Eventually, I found a good time for tri-x & XTOL, one that gave me negatives that just printed themselves.
THEN I went back to trying other developers. I made a side-by-side test of tri-x in Perceptol 1+3, DD-23, and XTOL 1+1. I could finally see the effect of the developer!
I decided to stick to tri-x and XTOL because I really like it and I can buy it anywhere. It is also my baseline for further comparisons. XTOL is also good with pretty much anything in 35mm, so now I always test a new film with it.
My conclusion is: if you want to experiment early in the learning process, experiment with different films. They are responsible for 90% of the final look. Once you nail a proper dev time for a film and a standard developer for that emulsion, then it makes sense to fine-tune your results by switching developers.
On the other hand, trying everything in a slapdash manner eventually teaches you that you NEED to work more consistently. It's good to make errors, too.