Cartridge Set Up Essentials

Endless. Suggest you watch one or two of the great videos Michael Fremer has on this, free on YouTube. 

As for me, having tried a few and studied a lot more, the only ones truly "essential" are the stylus tracking force gauge and whatever overhang/alignment jig you prefer. These can be downloaded and printed out for free. But if free rubs you the wrong way then the one I recommend is the Mobile Fidelity Geo-Disk. This has the advantage of being the same thickness as a record. You could of course simply lay the paper printout on top of an LP, same difference.

A lot of guys will freak, but you can get just as good results with $20 worth of the Shure stylus force gauge and a sheet of paper. This is coming from a guy with a Koetsu mounted on a Conqueror on a roughly $20k front end. Images like nobody's business. Done it both ways, love the Geo-Disk for its simplicity. 

As for eye strain, any dime store magnifying glass will take care of that. Not that its needed. Believe me, that last little fraction of a millimeter, that's not where its at. So probably most essential of all is a sense of proportion.

Along with the MINT, I bought a recommended magnifying glass.....much easier and more accurate.

The Dr. Feickert protractor, while really expensive, is the best I have used.  
A digital stylus gauge that measures to 1/100 of a gram makes it easy to dial it in.  
I have a Geo Disk and it works fine, but not as good as the Feickert.  I have not tried the MINT but as I recall you need one of theirs for each tonearm you use.  I have two tonearms and might add a third so the Feickert being universal is a better deal for me.  
I'd like to try a Fozgometer to dial in azmiuth, but I doubt I'll buy one anytime soon.