Rakshasha on Summit

For Summit, use your friend's servant. A level 90 with MLB sumo CE should be able to solo the stage. Use servants like Mash, George, Leonidas, or David (needs 1st Ascension) to protect your friend's servant.

For damage points, also rely on your friend's servants. The 2 BP - 3Mil is not too hard once you get a couple of hot spring CEs.

The summit’s the best for farming all event currencies at once assuming you don’t have many gacha event CE. But if you can’t clear it, the next best thing would be the Cave 40ap #2.