use a humidity guage for this. temp. make sure it feels right, I dont use a thermometer and the temp. is fine.
fo substrate, I would recomend paper towel on the bottom, mainly because when the prickly is adult, it will lay about 8 eggs a day, if you throw the dirt outside along with some eggs, you could have a MAJOR problem. if you want to use dirt, then make sure that before you throw the dirt outside, microwave it for about 5 mins. freeze it for 72 hrs, or just smash every egg. for light, just keep them by a window, make sure to have some shaded area though so when the phasmid gets too hot, it can go to the cooler section. you can also use a light.
for food, I put my leaves in a beer boddle filled with water after my dad uses it. I stick oak, or rose in and put it in one of my hanging cages I made. I mist them about twice a day because it seems they LOVE water.
make sure that when you have the leaves, there not old, and dry. alothough the pricklys will eat dry leaves as a last resort.
this is all I have for now.