Get a good steel rule, or 2. 15" - 24", and a 4'er. A carpenters square also.
Also, a set of marking tools such as a scribe and/or chisel tip.
I won a set of scribes from sawmill creek some years ago for making the 1 millionth post.
It's something I take very good care of, and made a cherry box for them.
If you intend on doing precision work, they are a must. Without, this would have been much more difficult to make.
Never, under any circumstances, consume a laxative and sleeping pill, on the same night