What about Rin's gemcraft? She must have a bunch of gems/prana batteries and I am certain we can expand on that very much?
Once we sort out our memories/abilities that is
Not really actually. Kirie tanked her family fortune on purpose because he's an ass.
Preliminary plan time, because having a plan is better than having no plan, no matter how bad it might be:
Okay... We need to grab the servant off of Shinji tomorrow. That's going to be our single biggest possible boon right now, especially because they'll come with an in-built prana battery in the form of Sakura. We can keep Sakura away from Zouken for a few days, he doesn't actually really care about that, and then we can grab her boytoy away from the war as well. She'll probably willingly help with that since we would want to steal his servant.
No... Better to make an alliance and
maybe steal his servant, probably Saber, later. While Rin and Sakura could probably support a 3rd servant between them, it's better to take care of Zouken first and then use the combined Makari/Matou and Tohsaka resources to build a couple of mana batteries. From there Saber should be able to go full power and, with Avalon, take on Gilgamesh head-on and win if need be. Nevermind the support Sakura's servant, ourself, and any others we can convince could provide.
I really don't know what to do about Ilya though. With Gilgamesh and Kirie dead we shouldn't have to worry about anyone jump killing her suddenly at least. I think we should be able to get her to realize what's his name was lying to her for a long time about her dad. That should at the very least buy us some time.
Caster
should just stay in their fort unless it's an odd one without a high Territory Creation. Hopefully it's a sane/reasonable one we can strike a deal with, between the two of us we could probably crack the Grail's system and show everyone it's been turned into the worst kind of monkey paw there is.
And possibly Bezet/whoever she summoned. Which could be a
really bad wildcard honestly. Bezet
believes in Kirei.
And, again, curveballs from the GM.