Man I have 8 SSRs like you do and out of those we have 8 in common, I'm impressed by such a coincidence (I have Acala over Summer Sol, everything else is the same)

None of the current Fire SSR would significantly improve your team right now, so I wouldn't recommend getting one for now. Ares isn't powerful enough to compensate the lack of debuff or party support, Acala isn't really good outside of auto-hitting and Enma synergies terribly with Amaterasu.
Make sure to get Mars when she come out around March though, that one's nuts.

I'd recommend either saving money, or getting an SSR for a secondary team (that's what you seem to be going for)

Considering the other elements, Satan and Amon Unleashed don't really synergies yet. They will with Satan's Awakening when her A frame def debuff will become elemental resistance frame, but that's not happening for a year. Anyways, with those 2 as starting SSRs, it'll still take multiple extra SR to make a satisfying team, and you can't even buy Dark Amaterasu (which is really good in Dark teams) with Miracle tickets since she's limited, so I wouldn't recommend going for Dark

For Water, the awkward thing is that a perfect Water team wouldn't use Ryu-Oh nor Aphrodite (because the Cthulu/Water Raphael/SSR Nike complete each other so well), but Ryu-Oh and Aphrodite are both really good Kamihime independently. Either Water Raphael of Cthulu would still be really good additions to your Water team. I'd rate Raphael slightly higher than Cthulu because Cthulu's A frame Attack debuff would overlap with Ryu-Oh, but I'm not sure if Water Raphael is in the range of the first Miracle Ticket. One of those would make a really decent Water team, and you technically have the option to transition to a "perfect" Water team in a more distant future (if you end up getting both Cthulu and Water Raphael from Miracle Tickets or gacha, then you have the option to get SSR Nike with a future ticket).

If you go for the last option, Light, the one you'll get is obviously Sol. Sol alone would actually give you a pretty decent team if you have Diana (SR), since Sol + Diana + Light Raphael + Amaterasu actually go together pretty well. In order to get a definitive strong Light team, you'd have to get Light Tsukuyomi too in the future though. The other advantage of Sol being that she's pretty useful in many other elemental teams too. However, the fact that you can't use Sol and Summer Sol at the same time will make her not that useful in your actual Fire team (I don't have Summer Sol, so that doesn't apply to me). She might be better than Summer Sol for some specific bosses in the future (especially after her Awakening), but she should be worse than Summer Sol most of the events.


Therefore, I would recommend to go either for Sol, or Water Raphael/Cthulu (I think Water Raphael is slightly better out of the 2 considering the Water KH you already have but I'm not 100% sure on that, they're close).

As for your jewels, I'd recommend saving them for either Light Tsukyomi (if you plan to go for Sol), Water Raphael (if you plan to go for a Water team) or the Saint Nikolas event where the SR will a really good Fire one (Raguel, A frame attack debuff for 15%)