I will add some more obtuse thoughts, for a first chisel.... Where to start???? 

Where to buy? Make it simple. Go to Lee Valley. You can get a set of 4 sizes for $75, or/and then, up to $430 for five that will do the same things. Bash construction framing, or tap at dovetails. However, one is more suited than another for specific jobs. But for now, don't worry; read on.

Why Lee Valley? Well, where you go to buy is up to you. LV just has more credibility and offers decent quality in multiple brands of hand tools. There is far more safety and security in quality then say, the-Bay or Big Grin with no protection, or quality. But, at LV quality and service cost; up front anyway.

The unseen, the hidden details? This topic can go a million miles and take hundreds of detours, so you want to be circumspect. Consider the most basic. Sharp. A two-by-four will crumble to the dullest blade, or chisel. A dovetail wants the keenest edge you can hone. Google "the unicorn sharpening method". You want fast! Unicorn it. You want cheap! Unicorn it. Need I say more? Yes! What about all of those stones for sharpening; all those motorized tables, wheels, and suckey devices? That's capitalism, and you are the mark with the wallet.

How long you stay sharp has a lot to do with the price of the tools offered. How long you sharpen has a lot to do with the hardness, and price, of the tools you choose. As someone who hand sharpens over stone, a hard steel is no faster at cutting than a softer one requiring more sharpening more often. In fact, hard steel is so bad I will avoid using it in order to avoid sharpening. 

Another factor for the circumspect buyer. When you get a cheap set of tools this means there is a certain amount of work in "tuning" them to be good enough to work properly. Trouble is, one needs to know what to do (and, see) to fix what's wrong. For this reason alone, go for the tool that is midst of cheapest and costliest. I hear Narex, low end of midst, brand are rife with tuning opportunities. They have decent steel however. Going to European brands includes hundreds of years of experience in optimising sharpening and use. They just come in exasperating metric sizes; unless you don't care, but be aware one size (metric/Imperial) almost requires matched tools.

A one-off size tool is fine. However, second hand can be a costly mistake that lands you in the cheapest of the new bracket. A set of four tools is a decent number to launch with.

I think this is enough information to avoid too much fear and confusion.

Oh, don't look for any chisels in the brands mentioned here. You won't find any but the cheapest. Post Pandemic--and pre/while-unavailability is the advertised culprit.