Hello! 30 gallons I believe is around 100 litres or so.... I'd suggest checking out this website; (Link is not visible to guests. Please register to view.
If you in put your tank details, filtration details and from the side bar click the option for 'Display species only suitable for my tank' and search for the fish you want, you can add them and the advisor will help with a rough stocking level
Generally the species you mention, I believe are shoaling species and need to be kept in groups of 6 or more, the website will tell you if a shoal is needed and/or if any species won't mix because of temperature requirements
I would still advise to individually research any species you want to take on for diet and other requirements, but as a start the website is a good one to get a rough idea