First you need to find what kind of cell you want to culture. Then you can find what kind of culture media from supplier you gonna need.
The common culture media as following:
For a ready-to-use culture media, you may also need to add Fetal Bovine Serum (FBS) and Antibiotics.
Resource: some of text from Sigma Aldrich
If last step is fine, you will see the bottom of the flask is hazy . Observe it with microscope, you'll know the approximate cell density. Here will teach you how to passage cell.
Resource: some of text from Rice