οὔτ᾽ εὖ πεπονθὼς ὑπ᾽ ἐμοῦ εἴς γε τὸ ἴδιον οὐδ᾽ ὁτιοῦν

this literally means: nor being benefacted by me with respect to anything personal. What could that possibly mean?

“… nor anything at all.”

I’m not sure what the problem with this is. Gadatas is surprised that Cyrus wants to help him although Gadatas has never helped him with anything private or anything else.

ok the capture of that fortress was not considered a personal benefit for Cyrus.