Hmm, if acquiring more firepower is his next agenda, i think it's better if he go to fate/ex universe. There he will participate in a holy grail war as master or servant, win the war, acquire the moon cell regalia, regalia is a powerful mystic code that can give the wielder authority over moon-cell mean he can controll it in a way. And moon-cell is capable to provide almost infinite mana, do calculation of magic in stead of his wielder which mean the wielder doesn't need to cast magic, and capable to support multiple reality marble which i think a good excuse for him to get a reality marble.
Melonic