Welcome to AA!
Items you need for a freshwater 35 gallon (I don't know anything about saltwater, sorry):
*API water test kit--you need this to keep your fish healthy. It will allow you to monitor the levels of toxins in the water which are naturally produced by decaying fish food, waste and the natural process of respiration.
*Prime water conditioner--all tap water contains chemicals that are toxic to fish. You need a good water conditioner to neutralize them and make it safe for your fish to live in Prime is the best in the market.
*good filter--the higher the Gallons Per Hour (GPH
) the better
*gravel vacuum--you'll need this to clean waste from the bottom of your tank
*substrate--Usually about a pound of sand or gravel is recommended per gallon. Whether you get sand or gravel will depend on what kind of fish you decide upon
Those are the basics to get your tank set up. Before you get fish, you'll need to do what's called a cycle, which means you'll be waiting for a natural balance to establish itself so that, once you have fish in the tank, some of the toxins their waste produced are naturally consumed by beneficial bacteria. Don't let the pet store tell you this cycle can be "created instantly" by "bottled bacteria." The bottled bacteria can help, but it will still take weeks to get the cycle going so it's safe for your fish. Also do NOT let the store convince you to get fish yet. You'll know your tank is ready when your water parameters read 0 ammonia, 0 nitrite, and low levels of nitrates. This takes time to happen and will require you to feed the cycle over the weeks you're waiting.
Lots of information above.
Once you've read through it, feel free to PM me with questions or to start a thread in an AA forum asking specific questions. People here will be glad to help you get launched.)