Before you go on a spending spree, start with a thorough cleaning and (proper) lubrication of the machine, and an assessment of all its operating capabilities (speed range, table travels and power feeds, etc.).
Then I'd get a good dial test indicator (like this:
Interapid (312B-1 / 74.11137�) �.���5" Graduation, Hand Tool, Dial Indicator | eBay , but make sure that it works correctly before buying a used one), and a precision level like this:
precision level by exact level and tool model 2�� | eBay (this isn't a Starrett, but looks close to the Master 199 level).
With the level, you can clean the table surface of any nicks and bumps by careful stoning and cleaning, then run the table in the full X-Y ranges with the level both parallel and at right angles to the table length, and "map" the errors cause by wear in the X and Y ways that can cause the table to "dip" on extremes of travel (especially excessive wear on full X left/right). This gives you a good idea of how precise it will cut longer straight surfaces.
It will also be handy for, ummm, leveling the machine itself (using shims under the base), so the machine doesn't rock and round tooling doesn't roll off the table surface - very annoying! Member Richard King has posted a lot of information on machine leveling and inspection, search for his posts.
The test indicator is used for getting other mill attachments square or parallel to table travels, or for more advanced work, setting up precision angles to axis direction. The classic example is tramming the head square to the table, and aligning a vise true to the X axis. Again, lots of posts here on how to do this.
And yes, get a good machinists vise, a 6" jaw width Kurt is sort of the "standard", but there's other options too. Don't cheap out here, a good vise is one of the best investments you'll make for your machine, a cheap vise will have you cursing every time you use it.
From there, cutting tools like endmills and drill bits, drill chucks, parallels, etc. Much money can be spent here, but again, quality pays. Watch Youtube vids on proper setup and use of endmills and drills, save yourself some cuts and broken tools.
And most critically, get (and wear!) good safety glasses. I instruct at a Cambridge technical university (small place on the river Charles, you wouldn't have heard of it
), and much of my time is spent reminding students to put on the darn glasses. It's worth finding a comfortable pair, and reminding yourself to use them. One forgetful day with a broken drill bit will literally change your life, and not for the better (unless you meet a really cute nurse in the ER).
