FGO 5th Anniversary Should You Roll? (TL;DR: Roll for Castoria)
Usually, this kind of note has my 2 cents on a Servant, but not this one. This one is the cold hard truth.
Source: Type Moon
1. Artoria (Caster)
Source: pixiv LucidSky 83845890
Castoria is a Support Arts Caster. ABSOLUTELY roll for Castoria. What are you, insane? If you are saving SQ then this is the time to spend it and I mean spend it. Like all of it. Castoria is so broken she is considered on par with Merlin in most cases. Usually, I recommended Masters to exercise some discretion with my advice, but to hell with that ROLL FOR HER. YOU WILL NOT REGRET IT. Assuming you get her, but with the amount of Free SQ we get you should be fine.
2. Leonardo Da Vinci (Rider)
Source: pixiv BORUMETE 72908381
Da Vinci is an AOE Arts Rider. She is essentially the SSR version of Rider Mordred. IE she is arguably one of the best Arts loopers in the game. I'm gonna be honest with you, I would recommend against rolling for Da Vinci unless you already got Castoria. If you have Castoria and need a good Arts looper, then maybe consider rolling for her.
I hope this was informative and bid thee Masters good luck