You might need a protein skimmer and it is best to go with a wet/dry filter, some anemones can be very hard work, its best to get a magnificent, tube, or rose tip anemone (Tubes being the easiest) Be carefull of some anemones like caribeans cause they actually eat fish and inverts (Inveratabrates, like crabs etc., etc.)
Sun corals would grow too big for your tank, I would go for a tube anemone with some live rock, and cycle with a couple of shrimp, (Damselfish cycleing takes longer) then you could get clowns once fully cycled (Tank bred common or percula clowns are the best, they are much hardier)
You will also need a hydrometer to measure how much salt is in the tank, salinity is measured in SG (Specific Gravsomethingsomething) you will need to aim to keep the SG between 1.020 and 1.025 (1.023 is the best)
Temperature is best at 78F. You will also need marine salt to make the water salty, duh!

lol, Ph should ideally be kept between 8.1 and 8.3 (As close to 8.3 as possible is best)