Pick the paid places first
The number of paid places sets the whole character of the event. Paying too few places makes the tournament feel winner-take-all. Paying too many places creates tiny min-cashes that can feel like bookkeeping rather than a prize.
For most social tournaments, 15% to 25% of the field paid is a practical range. Smaller home games often work best with two or three paid places. Larger club events can pay a wider ladder as long as the bottom payout still feels worth reaching.