New player here: how important is “meta”?

I’m new to this game, having gotten into it after the Crunchyroll release of Heaven’s Feel reminded me just how much I loved this universe.

I have heard that the most important units are supports like Merlin, Lady Avalon, and Caster Altria.

But I have also heard that their main usage is just to speed up farming. I don’t really care about that (I have a YouTube video or audiobook playing at the same time, so I don’t mind a fight taking ten minutes).

In that case, do I really need to prioritize saving for those units, or can I get away with just saving for ones I think look cool (ie the upcoming Medusa Saber)?

Will I be able to beat all content for full rewards (or at least close enough that my account can progress well) without those meta units?

FWIW, my current team is Altria (5*, from selector), Percival, and Emiya (Archer), with Hans Christian Anderson and Xu Fu as the two supports I built based on a tier list I found. I am 9 days in.

Edit: thanks for the suggestions!

I think my three priorities will be Medusa Saber, Scáthach-Skadi (Caster) and Altria Caster. After those 3, if I understand correctly, I should be good to entirely ignore “meta” for the foreseeable future (and all 3 are characters I like the aesthetics of; there is a reason Oberon is not on that list…).