You need a friend to use a summon monster spell, and as soon as the monster appears, you need to start the binding, because you can't concentrate on the summoned monster and cast a spell that takes longer than an action, as that takes concentration (see Longer Casting Times on page 236 of the 2024 PHB). That is a good deal, you get 23 hours of extra minion for the cost of one spell; sounds like it would be worth your buddy's 9th level slot to get the most out of the minion.
I think two casters could corral most outsiders they find on an adventure (and most adventures have at least one elemental, fiend, fey, or celestial in them). Caster 1 holds monster, caster 2 does the magic circle, and either of them can planar bind. Just remember that dispel magic was common in the at will or 3 times per day spell casting for demon lords and archdevils, so best to upcast the magic circle as high as you can.
Unless you are playing a one-shot, I wouldn't abuse planar ally. The best-case scenario is that the cleric's 6th level spell is now reduced to "summon mephit" or "summon dretch", because the god won't be happy with the cleric unless the cleric does something get back in the god's favor (want to guess which PC needs to die to make that happen?) or the god sends something to punish your PC (that was Plantar Angels' gig in 5e, and I wouldn't be shocked if it was now).