It so much depends on your circumstances. Are you going to brood them in the house? Are there predators where you intend to brood them? Common predators for chicks are pretty close to any animal that's bigger than they are. If you will be brooding them in the house where cats,dogs, or other animals can't get them, the easiest and cheapest brooder is a box, easily and freely obtained from your local grocery store. Put wire over the top because they very soon will fly/jump out and be exploring.. If you brood where the ambient temperature is in the 70's, then you wouldn't need to get a heat lamp, a regular, maybe 100 watt bulb will give them the heat they need. Raise or lower the bulb until it maintains at 95º (directly under the bulb) for the 1st week and usually lowering the temperature 5º every week after that. They must be able to move away from the heat if they need to. Always give them warm water to drink, cold water may give them poppy butt. If they get poppy butt, clean it off immediately and apply some olive oil to their butt, that will make it much easier to clean them off the next time. Give them chick starter, medicated. If you don't like the idea of mmedicated starter, then the next time try using without, but for your first time you want to be successful and doing everything by the book is safer until you get a feel for how things work. I don't bed new chicks on sawdust because I sprinkle their feed on the floor of the brooder( for the first couple of days) because it gets them eating right away. So I bed with puppy pads or textured paper towels. As you put the chicks in the brooder take a minute and dip their beaks in the water to get them drinking.They just need to get the water on their beaks, then they will tip their heads back to drink.
If you are going to brood anywhere other than the house then your idea of the plywood pen covered in wire is a good idea, just make sure its draft and predator proof and that you can maintain the temperatures for them. You will also probably have to get a heat lamp & bulb. Make sure its not teflon coated. The teflon coated ones emit toxic fumes when they are heated. Good luck and enjoy your chicks.