What kind of "party" do you bring a d20 to? I think your experience might be an outlier, most of this advice seems extremely pertinent to the events I go to.

Adventuring parties, obviously.

As long as you have a cleric you're good.

Maybe you are the outlier. Most people are not New York socialites, and aren't in college wandering into frat parties. Or perhaps there are many different ways people live, and "cocktail" parties are just one of them?

Sounds like the parties you go to may be way above my budget level - both monetarily and socially.

Birthday parties. Cool ones, at least.