You can make a wonderful reef from a small tank. Just remember, things you put in the tank when they are small have a tendency to outgrow the tank. An anemone in 30 gallon tank is going to take up at least half the tank, not much room for other corals. If you want a pair of clowns, go for Perculas or Occelaris, preferably tank raised. These clowns stay the smallest and are much more docile with tank mates than a pair of Maroons, Tomatoes, ect. Breeding clowns will defend their territory pretty vigorously, though.
Many people are drawn to SW by the image of clown fish nestled in an anemone. They do look cute. However, as was said, they don't need an anemone. If they feel like hosting with something, they'll "adopt" darn near anything as a host.
Mushroom corals, polyps, brain corals, colt corals, featherdusters... You still get the look without a difficult to care-for animal. Not all clowns will host with all anemones and some of their natural hosts in the wild are notoriously difficult to care for in our tanks. Research is key. The book "Anemonefish and their Host Anemones" by
Joyce Wilkerson is a good place to start.
Do some reading, and if an anemone really is your goal, figure on waiting at least 6 months for your tank to mature. The initial nitrogen cycle is just the first phase in tank maturation. I'd go with a single 250 w 65K or 10K bulb with power compact actinics on a 30 if it were me and I was thinking anemones or SPS corals. Ditto on ditch the canister filter but go with a skimmer and at least 30 lbs of rock, more if you aren't going to go with a deep sand bed.
Welcome to The Reef Tank. We're here to help. Please feel free to ask questions as you go along. We've all made mistakes here and hopefully, we can help you avoid many of them.
Alice