I usually type with a keyboard when I play but sometimes I'll lie back on the sofa on my own to do something low stress where I don't expect to talk, and someone from my FC will suddenly appear and try to hold a conversation with me. At these times, I've found some simple words/sentences which would really help communicate are nowhere to be found in the auto-translate tool. Namely:

Yes. (There are situations where 'Yes, please.' is a highly inappropriate answer!)
No. (Ditto with 'No thanks.')

I'm sure there are more, but those two annoy me almost every single time.

It would also be the best thing ever if there was some in-game way to see what your auto-translated phrase looked like in the other languages, in case the nuance is completely inappropriate or if you're looking to find お疲れ様でした and do not in any way, shape or form associate it with 'Good game!', a phrase I have never once in my life said in English