Baby things needed ?

So I’m a first time mama !

As I’m currently 21 weeks and 1 day...

This little guy will be the youngest in my family as my cousin was the youngest which she is 18 now !

Wondering what things should I start buying already ?

I have a full box of newborn pampers already.

Best friend has bought me a playpen with a changer and a sleeper that both can be removed for the baby to use as a toddler.

What things are necessary and what things aren’t ?