Start with starting a job on a submission and the two messages almost every form needs: a notification to staff and a confirmation to the person who wrote in, each built so that a reply cannot turn it into a spam relay. Creating records from a submission comes next, worked through in full for a person record, then a lead and a custom entity record.
Pushing to a CRM and taking payments both cover work a submission must survive even when another system cannot: an idempotent push that re-sends until the CRM confirms it, and a payment element whose settings do not always do what their names suggest.