I also find 2c-i to be one of the most nauseating psychedelics that I have tried. It's the only one that has actually made me throw up during the come-up. But after that, it's smooth sailing.
I would agree with e1evene1even and try to ingest your dose over a 15-30 minute period, rather than just taking it all at once. Although I have never tried this myself, it makes sense to me that spreading it out like that would be easier on the stomach.
Of course, I could be totally wrong. But it's worth a try
Good luck!