research! research! research!
yes start with a book, search threads, etc etc. as much as you can so you dont get taken advantage of at your LFS - local fish store.
if you dont learn in this hobby, you pay.
you will need a tank, a stand,
lighting, what do you plan to keep? a canopy? will your fish be prone to jumping?
mechanical filtration, in the form of a protein skimmer, media paper
biological filtration such as LS, LR, a wet/dry set up, refugium
things to keep your flow optimal , like powerheads
UV sterilizer if you want one - you could add this later
there are many combinations and choices you can go with, it depends on what you want to keep...
sounds to me like you are thinking of an aggressive tank, with eels and puffers...