Arts or Buster?

Just looking at the servants you listed, you lack a single target Lancer, so got for Kiyolancer/Tamamo. Plus summer mordred is in the same banner.
You don't always need a Arts team to spam NP, look at Jack and Tamamo lancer, their NP charge up pretty fast even not in arts team.
The idea is not whether to have a buster team or an arts team, it is what you are fighting against. With your servants, if I am fighting against lancer, I would not force a arts team. The idea is to pick your attacker for that stage and build around him/her.
And if you want to spam NP, just bring a kaleidoscope

Well if you like playing with arts team go for it, the game isn't nearly hard enough to where it matters what you pick.

You can already make a couple good arts teams off the back? Well first off you already have the premier arts support in tamamo and you already have 2 great damage dealers with her in Orion and shiki. So yeah just use them and for general use a support waver or tamamo to nuke something with double fox's wedding. You don't have to go full arts team remeber, so have hercules and other survival servants in the back.

As for the rolling you really don't need it (Unless the like the characters). If you want to roll purely from a game play perspective then you could try for either archerturia best arts archer in the game (but not needed since you already have orion) or merlin for the buster memes.

Also, don't be afraid to run a mix of both or so, no one can give you a team that can purely beat every single event and mission since class advantage is a thing.

I mean I got through most of camelot just using orion/tamamo/waver and for certain fights against lancers/rulers I would switch to (support) waver/jalter/hans with in both having herc(no bond ce) in the back and other survivors that could replace hans or jalter.

Emiya and Martha function well in an arts team with 3 arts cards. Also, agreed with the other response, not really much need to completely build a team around 1 card type, rather use the best you have against any particular enemy. And yeah, rider Mordred and Kiyo lancer/Tamamo lancer are in the same banner.

BTW, most importantly, if you really want more arts servants that badly, roll specifically for them. Not a great idea to depend on chance spooks to get specific servants.

On a completely unrelated note, I'm jealous. I've been dying to build a good buster team but almost everything I have belongs in an arts team.