How do you know if it actually worked?
"Forty people came" is the number that goes in the update, and it tells you almost nothing. Forty people came to what? Would any of them come again? Did anything happen?
Here is what's actually worth writing down, and it takes about ten minutes.
1. Who came, against who you invited
Not the count, the fit. Go down the attendee list and mark each one: right person, adjacent, wrong room.
A dinner of eight right people beat a dinner of twenty where six were right. If your ratio is poor, the problem is upstream in the invitation, not the promotion.
Track the show rate too: confirmed versus arrived. Under 70% at a free event is normal. Under 50% means your invitation is attracting people who were never going to come.
2. What actually got said
Write down the three things you heard that you didn't already know. Genuinely write them, a note on your phone on the way home.
If you can't fill three lines, the format was wrong. That's the most useful negative signal an event gives you, and it's invisible in any dashboard.
This is also your content for the next month, and the argument that fills the next room.
3. Who followed up without being chased
Count the people who messaged you within 48 hours. This is the closest thing to a real engagement metric that events produce, and it needs no tooling.
Two or three unprompted messages from a room of twelve is a good evening. Zero means people had a nice time and nothing more, which is a fine outcome for a party and a poor one for a campaign.
4. What it cost, per right person
Total spend, venue, food, photography, your time at some honest rate, divided by the number of right people who came. Not by headcount.
This number is usually alarming the first time and it should be. It is the only way to compare an event honestly against any other thing you could have done with the evening, and it makes the case for smaller and sharper rather than bigger.
The question that predicts the next one
Ask three guests, the day after, in a personal message:
"Would you come to the next one, and who should I invite?"
The answer to the first half tells you whether the evening was worth anyone's time. The answer to the second half is your next guest list, from someone who now understands what the room is for.
A guest who names two people tells you more than any survey. A guest who says "yes, definitely" and names nobody had a pleasant evening and isn't coming back.
What not to bother with
Post-event surveys with rating scales. You will get five responses, all 4s and 5s, from the people who least needed asking. Three personal messages beat fifty survey rows, and they continue the relationship rather than ending it with an admin task.