I would try like a 45 or 60 watt and test the temp with those bulbs. I would keep the temp around 85 degrees or so or a little higher is ok. If you see your cham gaping while basking then it may be too hot. The males usually have a bulge where their vent is. Sometimes it is hard to tell though. The coloring can be decieving when they are young also. Females are usually, orangish, peachy colored when they get older versus the males which have all the reds, yellows, blues, greens etc. Best is post a pic and make sure to take a clear picture of the vent/tail area and we will see if it is a male or female.