Our mini cushion moss terrariums come with their own grow light so they do not need any additional light. The light has three settings we have the brightest setting on for 10 hours a day. You need to turn the light off so the moss can rest!
While there are small vents there is not much airflow so you wont need to water very often. Typically we only water our mini terrariums once a month with RO water. You may have mold issues, that is normal!! You can prevent mold by allowing your moss to dry out a little between waterings or having springtails.
Occasionally you may want to clean the glass, this can be done gently with a paper towel and tweezers. If you ever over water your terrarium you can gently tip it to the side and use a turkey baster to remove the excess water, the remaining water should not exceed the pumice layer.