I am wondering what you mean by a competent tool set.

I would suggest if you deal with rigging get a rigging knife with a turnbuckle key.
For wrenches I would say a good adjustable, a pair of vise grips, and a ratchet handle with the sockets to fit what nuts and bolts actually exist on your boat.
You are not likely to be tearing down and rebuilding your engine at sea but you might need to fix a pump or tighten a fan belt.

I would also suggest spare sockets for the two most commonly sized and most likely to get twisted nuts you have aboard.