User blog comment:Someloser9/People's Picks for the Free Login Unit/@comment-26947994-20170809005050

If you have a decent team for hard content, I would recommend one of the really old units, like Lilith, Lilly Matah, Sefia, Kikuri, Elimo, etc. because 99% of the summon gates now are divine summon gates, meaning you won't be able to get those (and other) Omni units I just listed above.