I just built an incubator for last season and it worked great. As stated above, it depends on the number of clutches you're planning on having....think ahead. You may have one or two now and 10 next season. I looked at a number of youtube videos for ideas and talked to the local reptile shop guys before putting it together. Here's basically what you need.
Insulated box: cooler, mini fridge...I used an old full size freezer.
Heating element: mats, ceramic bulb...I used 11" flexwatt.
Thermostat: Your choice, can be fancy or not.
Fan (optional):Reduces temperature variance...I used 2 set at different angles.
Thermometer: I used 2, one on top and bottom shelf to make sure everything is working.
As for the little things:
Foil tape (different from duct tape) is used to tape the flexwatt to the back wall.
Old charger (phone charger or something to wire the computer fans) look at the power rating.
Insulating foam to fill the hole made for the wires... I made one hole and was able to fit everything through it.
power strip
drill and bit
containers for water (depends on size, fill empty space to prevent large temp fluctuations when opening and closing.
I'll try to post some pics in the next day or so to give you and idea. Just know that is really simple to build. Took me 45 minutes and cost about $150 or so. Maybe a little more. The freezer was donated. One last thing, get a calender so you can mark down the big day. Good Luck.