I would advise against an anemone as a beginner. They require just as much attention to detail as a reef aquarium does. Most would advise to have your aquarium stable at least six months and many as long as a year before trying one. I'd also wait on any sand-sifting species fo anything as they can sometimes be finicky, unless you're referring to a watchman goby. they are generally pretty hearty, but ask to see it eat before you buy.
What size tank do you have? I would keep only two clownfish unless you have a very large (150 gallon plus) tank. All clowns are born make with a dominiant fish turnign female. They tend to form a pair and then will not allow other clowns in their territory (generally the whole tank). In the tank, that means the less aggressive fish end up beaten up.
Please note, clowns do not NEED an anemone. Many captive bred clowns have never seen one and have no idea what to do with it. Many choose other items to be their host. I have an ocellaris clown that has taken up residence in a deresa clam, and ignores a long tentacle anemone about six inches away from the clam. In another tank, I have a cinammon clown who used to live in the long tentalce anemone, until I removed it when I put a hadoni anemone in that tank. I actively avoided the hadoni for at least three months until one day it just started cozying up to it.
Finally, whatever you decide to do, go slow with adding livestock and quarantine fish before putting them in your display. Almost everyone on the forum has gone through a round with crypt (marine ich). I'd say it's the most common actual disease in a saltwater aquarium. It's very treatable, but not with any inverebrates, live rock, or sand in the aquarium. It's a whole ot easier to prevent a mass infection in your display by treating one or two fish in isolation.
