The praying of tarawih is an important sunnah and really should be done. It should be prayed after the obligatory Esha prayer. For men, this is better to be prayed at the masjid in congregation, but it can also be prayed at home. Women should ideally pray at home, although it can be prayed at the masjid. There are varying amount that are prayed in various mosques, with the vast majority praying 20 units, but some mosques may pray only eight although they are longer units. We would recommend praying 20 units with the imam and praying the witr in congregation too.
Abu Dharr narrated that the messenger of Allah said: When a man prays with an imaam till he goes he is reckoned as having spent a whole night in prayer. [Sunan of Abu-Dawood Hadith 1370]
If however one wishes to pray a lesser amount, that is still valid. It is understood when the companions prayed eight collectively, they would go home and pray more. The honoured companion and second Khaleefah of Islam, Umar (may Allah be pleased with him) unified the prayer of Tarawih to 20 units in the mosque, and based upon the instructions of the prophet to follow the guidance of the companions, this has been the prevalent practice for many centuries.