Tips: Throwing the best parties

Both the host and the guest help the host level up.  Basically any activity that has a party balloon will help the party level up.  In addition, for party guests any activity that has a career or hobby icon helps the party level up.  Guest actions earn more party XP than host actions but they only get 10 and then they have to eat cake.  Hosts actions earn less but they use regular energy, which can be refreshed in the usual ways.  Hosts also get points for social introductions and actions which have no cost.  So hosts earn less per action but essentially can earn unlimited party points for the party as long as they are willing to spend the time.  Guests earn more party points for each action.

All of the actions you listed help the party level up except giving stickers.  We do that just to help each other earn gems.

The party rewards increase as the party levels up.  A level 10 party earns everyone gold, tickets and gems.

People don't get offended.  They need 6 of the "offensive" sticker to get full gem rewards just like they need 6 of the good categories of stickers.