Feeding:
I feed my plants when they are actively growing e.g. during the spring and summer with a standard inexpensive fertilizer (e.g. Phostrogen), adding a pinch to the water before watering. Unless you are using artificial lights feeding is not recommended during the winter when the plants are not growing.

However, note that a newly potted plant should be in fresh compost.  It will have plenty of nutrients, so there should be no immediate need to feed.  I don't feed plants during their first year. 

Generally, with the cultivation of any plant, it's quite easy to get carried away and over feed, and (generally again) this can be quite harmful to plants.