Hmmm..., bare essentials? To do what, exactly?
If what you intend is to do what the factories do with their basic loads, the list is simple.
Bulk components, including a versatile powder for the intended application.
A simple, rugged single stage press with the essential dies and shell holders.
A means to clean fired cases.
A good dial caliper.
I have had and used all of the more specialized equipment over the span beginning in the early 1990's, and have pondered 'the essentials' for that entire time. I have evolved (devolved?) to the stage that stresses simplicity.
My reasoning is that great factory ammunition, like Federal Gold Medal Match, is made on an automated line that simply precludes the possibility to do all of the niceties that reloading aficionados deem 'essential'. Yet FGMM ammunition's accuracy exceeds my capacity to exceed its performance regardless of my approach. I may not be alone in that.
There must be something going on here that basically thumbs its nose at the individual painstaking approach so many of us consider 'essential'. Hard as that may seem to determine, it's not. There is the attribute of consistency, which lends itself so well to mass production; i.e. KISS, but do it (religiously) consistently. In essence, if you can achieve success at load development, then the real task is to duplicate it without fail.
If that success has at its heart the unswerving commitment to complexity, then it may just be that we're building our foundations upon hills of sand. Simpler is more robust; simpler is better.
I accept whatever degree of concentricity my generic F/L dies can provide.
I accept that simply produced ammunition may need to sacrifice a degree of accuracy; and then I look back to FGMM and recognize that this is not a certainty at all.
I no longer clean primer pockets. I no longer trim/deburr, I simply mike the case length and cull ones with excessive length; reasoning that they all get culled eventually, and some just get there sooner. Dummy cases have to some from somewhere, anyway; don't they?
I leave the case necks precisely where they are when they come out of the tumbler.
More importantly, I address the factors that contribute most to case length growth. Chief among them is hotter loads. Who needs them? I don't, and I reckon maybe none of us does. They are attractive for all of the wrong reasons. They are penny wisdom, pound foolishness. They are built upon the premise that it's OK to work hard at wrecking our brass.
Simple fact; if the generic load can't do what you want to do, you're using the wrong chambering.
Consider this narrative and then ask your questions.
Greg