@shaqstudio
@nepalexpedition has a good list, but to add, I would say that the equipment to bring for a trek depends a lot of the nature of the trek.
Let me give an example - footwear.
Tropical rainforest treks are mostly muddy, river crossings, leeches, and stuff like that. On the other hand, because its "tropical", the temp shouldn't be a big issue (unless u are going high up).
So in this case, I personally recommend wearing regular outdoor adventure shoes (with a good grip), and be prepared to get it soaked wet! You can also bring along a pair of flip flops so you can dry your feet comfortably at the campsite.