Couldnt double vote for what I wanted.
Arena (both) should be the focus for any player. No I dont mean you need to be first, but your goal should always be to get to the best position you can comfortably with a mindset of daily income.
No need to worry about making a jump that will not net you more crystals.
Crystals are the most flexible currency you can get and therefore the most beneficial.
Both of those game modes feed into GAC and TW, for a trickle down benefit too.
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Beyond the above reasons, the general benefit of "meta chasing" is it will lead you on a path that has you investing in high level toons, that can be filled in later with others you can work on, "on the side" that will help with other game modes and events.