Don't try to get a compliance certificate at the last minute. Preparing for and conducting an audit such as for PCI DSS or SOC 2 from start to finish is a lengthy process, ranging from six to twelve months for most startups. Starting early and maintaining compliance is cheaper than starting late and doing rework.
This is basically the opposite of the advice I would give a startup. SOC2 attestations in particular are easy to get, and are a waste of money to obtain preemptively before there are purchase orders on the line for them.
There are things you should start doing early that lay the groundwork for attestations, but you should be doing them anyways, even if you never plan to get a SOC2 (and if a big-ticket customer never demands it, you shouldn't SOC2). That's stuff like setting up single sign-on and having protected git branches; simple best practices.
Anyone else want to spot check other parts of this document? I wouldn't feel qualified to challenge most of it.