I'm guessing the tank is about 30inches long x 12 wide and 15 high
When the filters are established you could have 10 neon tetras, a pr of dwarf cichlids (rams or something along those lines), 4 normal sized corydoras catfish (more if you have pygmy corys), and a pr of small labyrinths (honey dwarf gouramis or something similar).
This would be if you fed the fish twice a day and did a 1/3 water change and gravel clean each week. If you only wanted to do water changes every couple of weeks you would reduce the number of fish in the tank or cut back the amount of food being fed.
It also isn't a list of what you have to have. It is a guide and you can change the neons to harlequin rasboras, the rams to Apistogrammas, the corys to a small suckermouth catfish, etc.