*look up "rolling tricks and tips" on google (but do not do that game where someone hugs you as hard as they can and you pass out- use common sense when following tips to avoid health issues/death, clearly)
*fun lights, candles give off an especially nice glow
*chill music- not everyone wants to listen to techno and hardcore while sitting at home on a pile of blankets! I put on jazz since it seems to offend no one, but try to choose music that your group will like
*get out all the blankets and pillows, put them on the couches or the floor
*candies and fruits if anyone wants to snack (though that's doubtful)
*go to the local dollar store and grab as many things as you can find that smell nice (like essential oils...these are even better if you buy the slightly more expensive, high-quality ones from a head shop, spa or hippie store), or are cool textures. Nice textures to feel when you're high, of course, are rubbery, flexible, jiggly, or furry
This is the only way I roll, I almost never go out because the experience at home with fun effects and good friends to bond with is just so much better to me! Think of ways to stimulate all of the different senses. It's really about the conversations you have, anyway, imo
Make everyone comfy and cozy and enjoy the good vibes!
As far as numbers, I went to one or two larger house parties where everyone (15 peeps?) rolled and it was a BLAST to go from room to room and chat with different people all night, but generally I prefer to keep it to about five so it's more intimate. Do whatever you like, as long as everyone there is chill it's going to be a great time!!