http://www.go2itnetwork.com/making-wicca/
How do you make your own Wicca tradition?
I want to do one were you worship poseidon. Any tips? I don’t want any christians on here going “jesus is the only way” as that was not my question.
Thanks 
Generally, you would probably look at other Wiccan traditions and pick the parts you like best and then borrow and adapt them however you like. Then you would mix in a whole bunch of stuff about Poseidon and things associated with him.
Since west is the direction usually associated with water in the Wiccan traditions, I suppose you might want to have your altar facing west, (a lot of traditions use east). In the Asatru tradition, the high priest uses a spear during rituals, I suppose you could substitute a trident, if you can find one. If you live near the ocean, you could hold your rituals on beaches instead of preferring to use groves.
Wicca & Paganism : Making Wiccan Wands