This issue is really hot at the moment, what with the imminent arrival of CS's latest book-The Anarchist's Toolchest. But I've wondered about how many/few tools we should keep ever since I read the 1st introductory books on woodworking, where the lists always looked dismally small. There was always that conflict between what the books showed as an acceptable collection to get the job done, and what people actually kept in their workshops. And to make it worse, I would always err on the side of less and my friend Manuel, who has inspired and influenced me is the opposite.
My conclusion is don't fill your workshop up to the brim, because that causes stress, but go more than what the minimalists say. A case in point: in the The Ananrchist's Toolchest, a jack plane is included in the list. I often wonder about what a jack plane actually is-I use a #5 with a slight camber for general work, another #5 with a 8" radius ground on the blade (I define this my fore plane) as well as scrub plane with a 3" radius. All three are essential tools in my workshop, even when I'm using power tools. Another reason for buying more than the absolute minimum is to get experience. In this way you will buy duds and gems, but you 1st need to get them & use them before you can arrive at this conclusion. I didn't think I needed a full set of cabinetmaker's screwdrivers/turnscrews, until I got them. I can recommend these as essential tools to anyone. In the past, woodworkers worked as apprentices where they got formal training in an already established workshop (that of their master). We hobbyists don't have either. We have to stock up our workshop with trial & error.
Before someone reads my 1st blog where I advocate not buying too many tools, let me clarify. As a beginner you can get overwhelmed by the variety available out there. So what I mean is start slow and with quality in mind. But when you have most of your tools to enable you to function, then you should, in my opinion, be prepared to experiment with some tools that may not seem like essential. You might be surprised. You can do this without actually buying the tools just by visiting a friend and seeing what he/she keeps. So because I have three jack planes doesn't mean I like to have too many tools in my workshop. I also have five smoothers; #3, #4, #4 /1/2 with a high angle frog (HAF) for difficult grain, a bevel-up smoother (BUS), for even more difficult grain as well as a #112 for the most difficult grain. And I use all of them and I couldn't do without any one of them. (And I've used an infill and wouldn't mind one of those either).
So where am I going with all of this? I don't know and I am allowed to say this because I am a beginner. I am veering to the left and to the right in an attempt to find the middle road. I guess if the tool is used (frequently or not is NOT a factor), and if you either cannot do without it or you work better with it, then the tool becomes essential. I also believe that there are a lot of superfluous, unnecessary tools out there (I've said it before-look out for re-hashed tools.) But you have to make some mistakes in terms of buying an unnecessary tool now & then. But the knowledge you gain is worth the money you waste.