This thread is making me laugh. :) lol
Having the test kit will not only help you with your water hardness, but it will also help you on your need to make sure your tank will be cycled. Most important things in a community tank or a tank with more than 1 fish; Cycle & Quarantine.
The number of girls all depends on your other inhabitants. If you want cories, let's say 5. The number of girls will need to be 7-8. If you want tetras which need a group of 6-8, the number of girls will need to be 6 maximum.
Add as many decorations/plants as you can put in, also make sure it's to your liking.
Cories, tetras, some small loaches, even snails or shrimp will be good tankmates.