All transcendence levels are now the same, +20% atk/matk on weapons per level, and +20% p.def/m.def on armors per level.
Use https://tos.neet.tv/ to know how many Blessed gem you need per level.
They recently implemented it: just look up for the equipment you want to improve and there’s a little blank box below it, insert the desired transcendence level one at a time (0 - 1, 1 - 2, 2 - 3, etc) and you’ll know exactly how many Blessed Gems you need per transcendence level (1x Blessed Gem is 10x Blessed Shards).