Sorry to say that those fish aren't going to work. You could get 3 cardinals, but those would be the only fish in there. Cleaner wrasses are difficult to keep, usually best to find one that is trained to eat frozen food, but a great alternative would be a cleaner shrimp. They do the same job and when you put your hand in the tank he'll try to clean it! 18 gallons isn't enough for a dwarf lion, 30 gallons is the min. Plus there's always the possibility that the lion could eat the cardinals if it's able to. Cardinals are nocturnal and don't move much so they are easy targets.
Online stores w/ quick stats/info:
Aquarium Fish: Tropical Freshwater Fish and Saltwater Fish for Home Aquariums
Buy Saltwater Fish & Coral - Marine Fish, Live Coral, Salt Water Aquarium Fish, and Tropical Fish from BlueZooAquatics
No fish needs a certain coral and if you have a FOWLR
(fish only w/ live rock) you don't need any type of special light. If you're getting corals then you will need a light that can grow corals. You'd need a shorter light than people with say a 20 long. That means less money. Frogspawns are awesome. They are LPS
corals (large polyp stony). I'd recommend starting with soft corals, like hardy zoas and mushrooms. Then get LPS
and maybe even SPS
if you have enough light and good water parameters (montiporas are the easiest SPS
Lastly getting a filter twice your tank size would be ideal. Aquaclear is a great filter company so I recommend those, but really anything will work. You don't need a protein skimmer, just keep up on water changes (10% weekly is good). Finally, RESEARCH! Don't buy anything until you do and make sure you know what you're getting yourself into. It's very addicting and expensive and a whole different world than FW
. Best of luck!