Aside from the basic requirements to cruise (which are Rudder, Steering, Sails, and Good Rigging) there are plenty of other accessories which are good to have, but not required to keep the yacht sailing along.
First and foremost is a good dinghy. A dinghy is more than a small boat that rides along on your yacht, for it is your connection to the world around your yacht. If you pull into a harbor and wish to go to dinner, how will you get to shore? Water near the shores edge might be too shallow for your keel. Do you really want to swim and arrive soaking wet? Nonsense! Your dinghy will get you there in a safe and dry manner.
A dinghy should be viewed as an extension of your yacht. It can ferry cargo and crew to and from your yacht, as well as run or recover ground tackle into strategic locations which can be used to position your yacht or get it off a shoal.
Just as yacht designs vary, so do dinghy designs. There are some that look quaint but are fragile, and others that are practically a barge. The seaworthiness of your dinghy should be equally matched to that of your yacht, as you may find yourself working from your dinghy in less than ideal conditions.
If you run aground in a blow and need to run a kedge anchor out, you will have to brave the current conditions to get the job done. Another situation is if you are anchored and row into shore, then the weather changes for the worse and you have to get back to your yacht; now you have to navigate in sloppy seas. If you have a weak dinghy, this journey could be very challenging, but with a stout dinghy, you will truck right along until you reach your yacht.
On a much lighter side, a dinghy allows you the ability explore more areas for less money. If you arrive in a new town you wish to explore, your options to are anchor and dinghy in or pay for space on a pier. The cost to take a berth is charged by the foot, and the larger your yacht, the more you will pay for each day you spend there. On the flip side, it is usually free to anchor and dinghy in!
A dinghy is not crucial for cruising, but it will open up a whole new world to you.