Ms. M had quite an experience with greed. I wish she knew her Miss Manners by heart so that she had the comfort of knowing that she did nothing wrong.
The only types of parties where a gift is required are showers (including some housewarmings) and small children's birthday parties. Your shower gift buys you light refreshments and a chance to win the Grand Prize at the end of the party. Not that long ago it would been considered rude and greedy to ask wedding guests to also attend a shower. The Wedding Industry is deliberately confusing The Bridal Luncheon with bridal showers in an effort to swell profits. Yes, you invite people from the wedding guest list to a Bridal Luncheon or Bridal Tea, but you don't ask for or expect gifts. Yes, you require gifts from shower attendees, but the guests are a group of people who do not expect to attend the wedding and have volunteered to shower the bride with gifts and good wishes.
What is required from a wedding guest is a handwritten personal letter of thanks and congratulations. One MAY send a gift along with or instead of the letter, but this is strictly voluntary, not a requirement. Suppose you do this: attend the party and if you are entertained so lavishly that you feel a debt of gratitude, then send a gift? If the winng and dining are disappointing, just send the letter. Don't bring a gift to the party with you as hosts are too busy to be security guard, secretary, and cargo freighter.