I am new to the hobby too. But have read alot online.
I have 2 green chromis and 2 clowns in 30 gallon.. But chromis are schooling fish so do need atleast 5 Odd numbers always. IMO
keep one chromis and go for one more clownfish make sure the other one is larger or smaller than the one u have Or aggression will start I am sure u know that.
Its awesome to see them swim together and sleep side by side on the sand. They are like drunk sailer on the ground.
As far as more, u can have firefish. Depending on the size of fish and skimmer you have.
Hope that helped a bit.. Cheers.