An opinion isn't factual, yes you correct your wrong statements in the comments after you get the right info but then again how many people go to those?
About 2-3 turn Ragnarok kills / 1 turn Ultimate kills, BLITZKRIEG, If unfortunate soldiers as unorganized and commanded by a blockhead as were the Nazis could why can't you? No, but outside of jokes I started to play after you and I'm able to do these in all Advents, also solo all Raid Ragnaroks and the two available Disaster Rags; without saying doing AQ4 without Elixirs...
I've only spent 135$ on this game, that kind of says that with the right guidance you can "quickly" become a decent player that is self sufficient in most content.
Starter friendly doesn't mean "x" niche Kamihime is good or anything but regardless of that I kind of and don't agree with you on that; as a newbie you should prioritize the SSR Weapon before the Eidolon unless it's a raid/union event in which both are as hard/easy to get; also Advent events should never be mains unless they're the only one one has (Scrap Apocalypse and Phoenix though), they're normally useful and boast great stats for extra Eidolon though.