Why fish-in? It's way more bother than fish-less and in the end, you'll have to spend more on dechlorinator than on the ammonia. To top that off, your fish are likely to die which, if you don't care about their health, costs more because you'll need to replace them. Also you shouldn't use lights for a fish-less cycle anyway, so that would be one worry less for the time being if you change your mind.
Here are the must haves:
* liquid test kit for ammonia, nitrite, nitrate and pH (most important)
* filter
* heater
* dechlorinator
* plants (from my personal point of view)
Should haves:
* substrate (aquarium gravel or playsand)
* lights