Here's a brief summary:
1. Harem route (drugging), most content
2. Stopping the party - this option will become available later on. Second in terms of content.
3. Attending the party (without drugging). Little to no extra content, and fewer scenes during the party. No drama. The party happens and that's about it.
4. Not attending, no extra content at all
I recommend option 1 or 2.