Walk me through how you would model a pledge, a recurring monthly gift and a one-off donation.

All three use the same two-layer idea: the promise is one record, the money is another.

1. A one-off donation is the simple case — a Gift Transaction representing a completed transaction, with Gift Transaction Designation records if it is split across funds.
2. A pledge is a Gift Commitment with a Gift Commitment Schedule describing how it will be fulfilled, and a Gift Transaction for each instalment that actually arrives.
3. A recurring monthly gift is also a Gift Commitment with a schedule; the difference is intent and duration rather than structure, which is exactly why the model treats them the same way.
4. The reason this separation matters is that pledged and received are different numbers, and the board will ask for both. If you record the full pledge as a transaction you claim money you do not have; if you record only transactions you lose the commitment and cannot forecast or chase it.