The single decision that determines how much of it lands on you is whether card numbers ever touch your systems. Use a hosted checkout or a payment field supplied by your processor, where the customer enters their card directly into something the processor controls, and the vast majority of the requirements are satisfied by them rather than by you. Build a form that collects card numbers and passes them through your own server, and you have taken on a compliance burden that costs real money to satisfy and is not worth it at any small business scale.
What remains yours is smaller but not nothing. You will typically complete an annual self assessment questionnaire through your processor, which for a business using a hosted checkout is short and mostly asks whether you are doing sensible things. You need to keep the software on your site current, use strong and unique credentials on anything touching payments, and restrict who has access to payment systems. And you must never store card numbers anywhere yourself, which in practice means not in email, not in a spreadsheet, and not written on a form in a drawer.
The failure mode worth avoiding is the one that happens by accident. A customer emails you their card number because it seemed easier, and now it is sitting in your inbox and your backups. A team member writes one on an order sheet. Somebody sets up a form that emails order details including payment fields. Each of these turns a compliant business into a non compliant one without anybody deciding to change anything.
Fixing that is a policy rather than a project. Card numbers arrive through the payment page and nowhere else. If a customer sends one another way, delete it and send them a payment link instead. That single rule keeps you inside the simplest compliance category available, and it costs nothing to adopt.
Ask your processor which self assessment applies to you rather than working it out yourself, since the questionnaire differs by how you accept payment and answering the wrong one is not compliance. For a business using a hosted checkout the applicable version is short, and the processor will tell you which one and frequently walk you through it.