by the looks of your SSR, you probably should aim for light or dark. But if you have any 100% eidolons, you should aim for that element instead.
not fully sure on everyone to get but depending on element, these are some good targets:
Fire- Svarog, Mars, Amaterasu
Water- Nike Unleashed, Poseidon, Cthulhu
Wind- Titania, Aether, Cybele Unleahsed
Thunder- Raiko, Baal Unleashed, Jupiter
Light- Tsukiyomi, SSR Artemis (forgot the name), Sol
Dark- Thanatos, Chernabog, Amon Unleashed
the trick for newer players is to just join others raids. if you start your own and the boss HP isn't dropping, some players will think you're just AFK or something.
raid events (union ones too) are designed in a way so that all players can get the SSR rewards no matter how strong they are. it's just that newer players clearly need assistance since only standard might be a viable solo grind if anything.
at most you'll end up maintaining buffs, debuffs, and possibly some damage but to be on the safe side, just stop doing any actions if you're about to die.
and if you do happen to start your own raid, you can request union help only once, but "all" and "friend" help can be requested multiple times (once per 10 mins I think)