Scottish Gaelic:
* Ceart gu leòr, latha eile. (This is a fairly literal translation: "Right enough, another day.") This is informal and suitable for friends.
* Ceart gu leòr, faic thu feasgar/a-màireach. ("Right enough, see you this evening/tomorrow.") This is also informal but more directly addresses the "see you then" part. Replace *feasgar* (evening) with *a-màireach* (tomorrow) as appropriate.
* Math, gu bràth. ("Good, bye/until we meet again.") This is a bit more formal and suitable for acquaintances.
Irish Gaelic:
* Ceart go leor, feicfidh mé thú ansin. (This translates more literally to "Right enough, I will see you then.") This is a fairly neutral option.
* Go deimhin, go dtí níos déanaí/amárach. ("Indeed, until later/tomorrow.") This is a more formal option. Again, choose *níos déanaí* (later) or *amárach* (tomorrow) as needed.
* Okay, slán go fóill. ("Okay, bye for now.") This is a casual option.
The best choice will depend on your audience and the situation. Using any of these phrases will be understood.