|This build aims to be as low budget as possible by only using easily available F2P Units and turn Gunther into a fairly decent physical wall. Recommended for new players and people in need of a Green unit for their Horse Emblen Team.
His weapon should be Def refined to increase his decent physical bulk.
For his special, you can use Ignis, which you can get from Female Robin after obtaining her from her Grand Hero Battle(GHB). You can also use Luna, which you can get from Valter after completing his GHB. Alternatively, Bonfire from Male Robin or Adult Tiki is also a good choice.
For his A-Slot, Def +3 is recommended. You can inherit this skill from Stahl after completing his Hero Battle and upgrading him to 4*.
For his B-Slot, you can use Guard 2 to increase his survivability and make him able to survive Reinhardt. That skill can be inherited from Julius (GHB, no longer availlable) or common units like Leon and Titania. Alternatively, Lancebreaker 3, which you can inherit from Narcian (GHB), will help him beat most lance units in this game.
For his C-Slot, you can keep his hone cavalry if you want to use him in a Horse Emblem team or inherit Hone Atk 3 from Olivia, who is available from a Hero Battle.
For his Sacred Seal, you can give him Close Defence or Defense +1. Upgrading these Seals is recommended.
You can use Gunther to force Physical units to approach, as his Bulk is good enough to survive most green and blue physical enemies, as well as many blue mages, including Reinhardt if you use Guard 2. He is also a solid addition to a Horse Emblem team, in which his bulk can become incredible.
If you summon a Gunther, then +Def/Atk/HP are his best boons and -Spd is his best bane. -Res is also OK, but he'll be unable to survive Reinhardt, even if he has Guard 2, when he's unbuffed.