Beginning of the Journey CE

Actually it's never worth burning 4* for a CE most of the times and looking at your servants I can see you have some good farmers in Tama Cat and Frankie,Beowulf is a bit mediore but still viable and Anne & Mary can deal a lot of damage in both crits and NP because it's Single Target and I see you only have AOE riders so I would raise them and wait for a Fionn or Stheno to spook you and them burn only if you want,besides the CE effect it's not worth burning those servants or any servant in general

If you don’t plan on using Mary and Anne you could burn one of them for the CE since you have two. Honestly the CE is pretty useless though since 75 friend points isn’t much. I personally like having one of everything so I probably would burn one Mary and Anne to get it, but you’re not missing out on anything by not having the CE.

Wait for more Sthenos to burn. But that CE is lame, recomend save RP for Mystic Codes you lost (unless you lost absolutely none).

Fionn will get semi-useful in a distant future, a low-key NP charge in his chanced evade (who will have reduced cooldown by 3), and his clairvoyance will be increased and be AOE. So, he becomes okay as a farmer (of low attack...put Golden Sumo/Halloween Princess to fix that) and an arts crit support (CasGil is still better in every aspect).

If you will never use them I’d say burn them, I burned my 5* Altria for 5 rare prism

If you fancy yourself a collector and completionist then... probably?

It's not really worth it, for me at least. As mentioned, best to wait until you get someone like Fionn to burn, though I'd keep one copy of him and burn the 2nd and onwards, you never know when he'll become useful even if only on the back line for extra event drops.

That said, the better rare prism shop items at the moment would be the Mona Lisa CE and, if your lineup tends to be buster-crit, the Anniversary Blonde Mystic Code.

I'm not even considering burning 1 for a Mona Lisa... so IMHO, probably not.