Karma alone.

Every created being isa slave to its nature and follows its own natural disposition. The whole of this creation including gods demons and human beings have their beginning in nature. By the force of Karma the soul takes diverse corporeal forms high and low and quits them. Karma alone appears in the form of an enemy, a friend or a neutral and karma alone is our preceptor and almighty Lord. thus says Lord Krishna in the Maha Bhagavada purana. Therefore sticking to the varana and ashrama determined by ones own nature and performing one own duty one should duly worship Karma alone. In fact that alone is one's deity by which one lives happily in this world. Depending on a particular deity he who worships another does not derive happiness from the latter any more than an unchaste woman who loves a paramour.
A Brahmana should live by the Vedas a Kshatriya by protecting the Land A Vaisya by Varta (4 kinds agriculture, commerce rearing the bovine race and usury) a Sudra should live by service.