hi there, it's a very very good idea to have a Q tank, however I wouldn't say it's essential.
It does depend to an extent on some factors like the quality of fish shops in your area.
We're very pushed for space so we don't run a Q tank at all, but here's how you do it if you want to.
You need the usual equipment, filter, heater, lighting, you need a few bits of decor but generally no substrate and not heavy planting. Just some wood/rocks so there is some cover for the fish.
You don't run the tank 24/7, just run the filter from it on your main tank, then the morning before getting fish you fill the Q tank, rig the heater up and so on, move the filter over onto the Q Tank, go out to get your fish and just pop them in there. You then leave them in there for around 3 weeks, if no signs of disease have developed in this time then fine fish can go in the main tank, if something has developed then obviously you treat it thne leave it a few weeks until you are satisfied with the health of the fish. If there's been no problems then just move the filter back onto the main tank, clean the tank out and strip it down, if there have been problems then throw away the media and start with new (although this will need to run on the main tank for 4 weeks before it can be used in the Q tank) and sterilise all the equipment and the tank before it's next use.