Which servant for the 3m downloads campaign

Emiya's fine after some dedication, but he's not the greatest, consistent Archer. His NP is weak until Interlude and he has a weird mishmash of Arts/Crits focus, without much star generation outside of his NP and a super awkward Arts+ skill when he has a Buster NP. I like mine okay, but mine's NP is level 3 (to my dismay).

Martha's pretty bad unless you plan to pair her with someone like Fran or TamamoCat to cleanse their NP downsides. Her damage is terrible and her NP is pretty pathetic all the way around. She's good for supporting other servants who cripple themselves, but that's...kind of it. I'd stick with Ushi, if I were you.

Marie's not a damage dealer, either, but she's a good support. I prefer to use Alexander, honestly.

Get who you want, but the ones you're asking about here are all pretty meh. Carmilla's a nice option to increase that base damage. I'm personally looking forward to nabbing a Heracles, as Fran is my best Berserker right now.

Marie is a lot tankier than Martha though Martha offers heal support and in the future she deals more NP damage.

David's gimmick is only his evade skill so having Emiya is a nice addition to your team due to AoE NP and his strengthening buff in the future.

While it is good to have Carmilla at NP2, you may want to invest the ticket to the servants you don't have unless Carmilla is your main.

But in the end, Heracles will always be a top choice unless you have him already. Lancelot is mostly on farming team but Heracles is all around berserker due to his damage buff and survivability especially when with his bond 10 .

Speaking in a general sense, you should look at getting a Herc. He's arguably the best SR in NA right now and once you get his bond CE, he definitely will be the undisputed best SR for a while. He can carry you through various story and challenge quest. Lancelot is an AoE berserker so they can fill slightly different roles, if you're worried about that.

If you don't like herc then Emiya is another great option. Especially once he gets his skill upgrade, he'll be very strong. He'll also fill your AoE archer slot. He'll be very useful for you.

If you have your heart set on rider then I would say go for Martha. I belive she has a greater impact in the battle overall than Marie does.

Don't go for an Np2 Carmilla. She's great but you can get way more value by choosing one of the other servants I mentioned above. Or even the ones I haven't mentioned, if you don't have them. Only go for her NP2 if you have all the other good servants.