First off, it would help to know your local water parameters like pH, GH, and KH (hardness). From what I've heard of angels, they should be in groups of 5 or more. The rainbow shark needs to have a 4 foot (48 inch) long tank, so it wouldn't be suitable for your setup. Kuhlis and cories do best in sand, but they can live with smooth gravel.
We have most of these fish in our profiles. If you click on a shaded name you can see a lot of information about a fish. You can also seach fish by name when you click on "Tropical Fish Profiles" under the site logo. And welcome to the site!