A short list, in the order most shops should add them.
ESSENTIAL
Your payment gateway plugin An SMTP plugin, so order emails actually arrive A caching plugin, correctly excluding cart and checkout An image optimiser A backup plugin sending copies off the server
USUALLY WORTH ADDING
A security plugin, for login protection and file scanning A product filter plugin, once the catalogue grows An SEO plugin A shipping plugin, if your rates are more complex than flat rates allow
SOMETIMES WORTH ADDING
Abandoned cart recovery Product reviews with photos A bookings extension, if you sell time Subscriptions, if you sell recurring
RARELY WORTH IT
Anything adding visual effects to the shop Plugins duplicating what your theme already does Live chat, which is heavy and only useful if someone is actually available to answer
THE TEST
Would removing this cost you sales or time? If not, remove it. Every extension is a performance cost, a security surface and an update obligation.
