>>14055470I'd recommend Explorers of Sky/Time. Sky is the Emerald of the series, but it CAN spoil some stuff taken for granted though. Characters seem less up your ass though.
Blue Rescue Team is pretty good, but it can be a bit basic. I'd play it first if you get multiple PMD games, with the caveat that 2 is better in many ways.
Of the Ranger Games, all three are decent, but Guardian Signs suffers from being a bit too obviously linear and fetchy. It's got some good challenge mode stuff going though, even if it feels tacked on.
First Ranger game is fairly short and hard as hell since captures reset if the line breaks. This was fixed in the later games though.
Shadows of Almia is the best of the trio though. A nice long plot, plenty of areas to go, partner customization, and lots of quests to power you up.
As for Conquest, I still haven't beaten it. I just kinda got bored. Then again, my Japanese Black 2 came a week later, so...