I'll usually try to get tier one boots either after my completed jungle item or at some point during building my enchantment since there are some instances where some extra mobility would help me more than the finished product. It really kinda comes down to how much gold I have on hand when backing. If I've got enough for a dagger or two but not enough to finish Devourer's, for instance, I might just get a dagger and boots so I can roam and clear a bit faster a bit earlier.
If I'm doing well personally, I'll sit on tier one boots for another item or so. If I'm keeping even I'll usually try to finish my boots then to increase my roaming/defensive potential, and if I'm playing someone like Elise or Diana I pretty much HAVE to get Sorc Boots as my second item.
Boots for a jungler really come down to what you need at that moment, and for the next few minutes of a match, versus what would you be giving up. Finishing my Boots of Swiftness on Rammus, for instance, may increase my ability to roam but it isn't doing as much for my defenses as spending that gold on the Chain Mail component of a Sunfire Cape. If I think I can get away with it, I'll do it. If I'm worried, I won't.