Hello, check the Guides tab for PVP and farm teams.
There are multiple guides on PVP, PVP is based on just what characters you like and the offensives they have against other characters.
For your characters, I would use:
B Emilia, R Ban, G Gowther, and R Howzer.
In this order, that way if anyone dies. Howzer can aoe the enemies since they'll have low health towards the end of the fight or switch him with Ban and finish the fight faster.
Howzer should be the first priority in upgrading, give him Atk/Crit Dmg and he can run the PVE farm all day by himself. Gowther should be second for the dissolve after enemies turn so he stays alive with HP/Def. Ban's good for dissolve on your turn in case you don't have a Gowther card with Atk/Def. Then lastly finish Emelia with atk/def if she's 1/6 but atk/cit if she's higher than 3/6.