i am posting this to confirm it works and discuss it.

start with kageki, gateway, and any level 3

activate gateway

normal kageki, special level 3, overlay for M. x-saber invoker-gate is 4 c

invoker eff get any level 4 six sam but kizan, gate for kizan, special kizan-gate oat 2 c

overlay for shien, get kizan, gate for kizan in grave(used for shien eff), gate for grand master , special grand master-2 c on gateway

use 2 c boost grand master

field is 1 invoker at 1600, 2 XYZ shein at 2500, and 1 grand master 2600 at end