Board Thread:Questions and Answers/@comment-36170866-20180802160505/@comment-27971189-20180802163312

Its up to you, but IMO priority goes:

1. Saber or Lancer

As you can see it, their pool not having much option to offered on start but on higher rarity which would make it obvious enough, so having SSR from any of those two are good for starters.

2. Caster

Because chance of getting support trio of Merlin, Waver and Tamamo which would carrying your team. Fair pick of SSRs with mixed bag that are Scheherazade and Anastasia that requires late game materials to ascend.

3. Assassin

Because SSR Assassin is extremely rare. So having one is considered saving time in game unless you're OK to method like Palingenesis to buff Assassin of lower rarities.

4. Rider

Rider is class that nearly as good as Archer, where everyone is good pick even at lower rarities. Not a priority as even their lower rarities can perform good enough and they have fair amount of pick.

5. Archer

Class where everyone is good regardless of their rarities. Pick it only if most of the SSR Archers are your favorite characters.

5. Extra

One hell of mixed bag that looks tempting. If you get Jeanne / Jeanne Alter / Amakusa / Dantes, congratulation. Other than them? You need to be patient waiting until, at least, mid-game (or Babylonia) to understand their contribution. By nature they are premium units, pick them only if you willing to take risk whoever you got.

5. Berserker

Pick them only if you have interest to their SSR characters. Not that they didn't help or being worse compare to other, its just securing other classes is much better.