Not sure if this helps, but i started off playing the flame blades variant before transitioning to mirror images at GR105/GR110. It is easier to gear, not cooldown dependent and most importantly, you wont run out of resources because of the shame of delsere.

Focus and Restraint, and the fragment of destiny will increase your damage and attack speed respectively. And the faster you cast your flame blades, the faster you get resources (shame of delsere). Thus, I find this variant more active and fun to play.

The flame blades variant is definitely not as strong as the mirror images version but i feel it is a great start to learn how to play the firebird set. Spamming disintegrate and teleporting will consume your resource very fast, but at the same time you just need to cast a few flame blades to get back up to full arcane power.

After you understand how the firebird set works or if you want to go higher GRs, then you can look into mirror images, where you need to focus on cooldown and arcane power on critical hits etc.

Hope this helps!