No anemone in a tank that size but you could consider something like a hammer, torch or frogspawn if your lights are adequate.
IMO only one fish in a 10 gallon especially if you have many corals since some corals will sting fish. The less fish you have the more stable a 10 gallon tank will be. Make sure of your choice of fish you don't want to change your mind and have to tear up your tank completely to get the little guy out.
Get a good liquid test kit and don't add anything to your tank you aren't testing for.