There's no mention of pedals, you will need a pair of those. And shoes.

You will probably find yourself needing/wanting a new saddle. Be prepared for a long an arduous journey to find the one that best fits your ass. Ask your shop if they have a saddle test/loaner program of some sort.

Clothing. A nice bib-short (or knicker if it's cold where you are right now), is one of the best things you can buy for yourself.