Hi there:)
For your question, I would say Hydra+ Crius+ Atlantean+ would be the best lv50 armor, unlock them first, then farm the material to craft the +version armor.
*Unlock does not affect your currently armor, you need to farm the material to craft the +version.
Although the Living flame+ is not bad too, but consider that there are many enemies with fire and water elements, I would not recommend you to get that. And eventually, you will craft the Dark Prince armor, which is much better than Living flame, so choose Hydra+, Atlantean+ and Crius+ would be your best choice.
For Chimera stage, the element is earth/spirit, the best armor is the living flame, fire beats spirit and spirit beats earth, you can use the living flame armor, but no need to keep upgrading.
If you have any further question, free feel to ask:)