I wouldnt go for marine my self as there are more specalised and very expensive to buy and keep. Tropical are easier and if you get a good book to read up about setting up your tank are very pretty. some good starting fish are. Mollies, platies {BARE IN MIND THESE ARE LIVE BROODERS AND BREED FREELY ONCE SETTLED] and Guppies Neon and Tetras are all commual fish. Need to check as some fish dont do well with others. If you fancied cold water you could go for Fancy gold fish, cold water minnows [they need pump and filter] Cold weather louch. Dont know if im any help. For warm tropical fish you need Pump,filter thermostate, Water testing kits are good and water safe which you add to you water to make sure all the chlorines gone available at pet shops. Dont forget a thermometer. Gravel or sand and what ever ornaments you want.