Hi Kikinono,
For my homemade bator, I used one of those thick styrofoam coolers with a tight fitting lid. I think it had been used to ship Omaha steaks or something. I tried different lights, night light, regular bulb, etc. I watched the thermometer & hygrometer (got both of those at the pet store for about $5) and experimented with different wattages until the temperature was right and stayed that way for an entire day. I ended up using a 9 watt bulb. I bought my fertilized eggs from a nearby farm. This is my first experience with any kind of poultry farming. I live in the city and have had to give most of the flock away, but we love having our remaining tiny little backyard "flock" and eating fresh eggs!
I do not pretend in any way to be an expert, but I just purchased an inexpensive aquarium hygrometer and thermometer set, used stuff that was in our garage, and spent less than $10 total on my bator. I was not terribly fussy or precise and had a great experience with my incubating/hatching. My chickens are Ameraucanas and lay green eggs.