if i am DMing ........
you most likely live in a world covered and caves and ruins mostly left uncharted and unmapped. the art of adventuring has been a boon on the world as people go in seek riches, fame, and clues to the sinister history the their world.
also a secret war rages under the feet of this more or less happy world the evil that once ruled this world still sleeps with in it. his slaves still carry out his wises to tare down hope and kill the gods that imprisoned him.
some notes for your PCs
-abilities scores and hp. use a 25 point buy. your hp is your full hit die pulse con mod per level the 1st 2 level every level after that you add have your hit die pulse con mod per level
(so a lvl 4 alchemist with 12con would have 28hp. 8+8+4+4 for each level +4 from adding con mod per level.)
-gods. if you worship a god you need to make them from the list of domanes, this in clouds the god temper and goals. in most cases a god only is worshiped by one group of people like a part of a city, town, or tribe.
-poison. poisons are not seen as evil and the use of witch is no more evil then using a hidden dagger the cost of all poisons are dived by 10. if your class says you may not you poisons then it is still a dishonorable ack for you.
-guns. in games where i use guns follow the rules found in the dragon mag#321 "way of the gun" by Micheal Shortt.
-races. assimars, tiefings, and base drow are all base races and i have no problem with them
all though if you do choose assimars you must have a -2 in str or con your pick. all other race must be cleared by me.
-books. the Pathfinder Core Rulebook and the Pathfinder Advanced Players Guide are to be used when making your PC you may use other books but they must ALL be cleared by me as well.