Minecraft – Do villagers always sell first

Trading is random. Period. If one wishes to trade with any kind of reliability (and I use this word extremely loosely) they need to expand and defend a town to mammoth proportions and trade with everyone.

When you perform the only trade a villager offers it expands that villager's trade options, so with enough villagers, all traded, you get many options. If a villager offers multiple options, you must trade his newest option to expand his offers further. Thanks @Kevin Reid for this tip. You don't always get the trade you want, but this greatly increases the chances of doing so.

I should note that sometimes villagers CHANGE their options, which means a trade you really want may not always be available, even if it previously was. The good news, is that villagers only change options or add options when you make trades. So if you have a trade that is too valuable to loose, it would be best to save as much currency (whatever the villager wants) as possible and make a single or few large transactions rather than many small ones.

TL:DR: Trading is not reliable therefore it is not always cost effective.

There are a few stories I have heard like this, there are a few possibilities: 1) Zombies have attacked your villagers. 2) The villagers despawned Ahh, villagers aren't supposed to despawn, but I have heard stories, one story heard says that this occurs when you download mods, as a glitch. Also it might occur if you have a mod that is SUPPOSED to make villagers disappear! Since you have mods, the mod being the fault is likely, but not 100% so. For example, If you switch between game modes or difficulties, there is a glitch that causes villagers to despawn. Hope this was helpful!