If you want the over all flow of story it would be Langrisser III, I , II, IV, and then V. However III, V have no fan patch, but both have text translations. I would suggest however just playing via release date so I-V, and even then if Japanese isn't an option skipping 3 is all right. The battle system is odd and is set before 1-2 and 4-5. But some consider the story excellent.
Each game is playable on their own but do reference the other games. Ledin and Sieghart can appear in Der Langrisser. Jessica is in all of them. As are other references. Even 3 has tidbits that may be enjoyed slightly more having played I and 2 prior.
Most of the games are set at least 200 years apart. III maybe longer and V is shortly after IV. IV is also on a different continent, but that does reference a few things from II.
But again each game can be played on it's own and enjoyed.
As for versions honestly what ever is in English I guess. Warsong will give the story of Langrisser 1 with bad names, but the translation isn't actually bad. The english PC fan patch will give slightly more story, right names, but is harder to set up.
Langrisser II md and Der Langrisser each have good and bad things. Story wise go Der Langrisser, gameplay personally for me its Langrisser II MD.