Hi Caz27,
The quantity of fish you can put in depends on the volume of your tank. If you post the dimensions we will be able to work out the total length of fish you can safely stock - bear in mind you will need to build up the fish over a period of time so that the filter bacteria can cope with the load. What type of filtration are you using on the tank?
As to what type of fish - that is going to be difficult to answer. The best thing to do is have a look around, maybe get a good tropical fish book, and come up with some ideas as to what you would like. Then if you post it here people will be able to advise on what will and won;t go together.
HTH, Eddie