Tbh, I prefer to have a collection of all element Kaiser before I go for LBing the ones I got from gacha. In fact, I had wind & thunder Kaiser from gacha before the orb shop & I've bought light, dark & fire Kaisers, moving onto water next. Those actives are valuable at the end of the day, arguably the best ones in the game. LB0->1 a Kaiser will only bring you a bit of stat increase (about 100 HP & 400 atk) & 10% more elemental value for the corresponding elemental if summoned. Whereas buying a new Kaiser will bring you 30% dmg cut and higher debuff resistance against the corresponding element for a little bit of stat loss. So yeah, that's my standpoint on Kaisers, at least.

Oh, on a side note, those interested in tower might want to consider working on water Kaiser since the first (fire) tower supposedly arrives in 2 months.