An old thread, but here are my thoughts for future reference.
Entreri is typically seen as a Fighter first and Rogue second, so I think using the Fighter class is the best bet. At lvl 2 I would pick up Apprentice Sneak Attack.
Weapon Focus: Ruffian gives access to stilletos and sabres, both of which are good options for Entreri. There is a lifesteal stilleto in lvl 1 of the dungeon beneath Caed Nua.
Other useful talents would be Vulnerable Attack and Two-Weapon Style.
For Fighter features, I'd say Confident Aim, Weapon Specialization: Ruffian, Armored Grace and Unbending are good options.
Entreri is obviously human, so that's an easy pick. For culture, i Old Vaila is probably the closest to Calimshan. Drifter, Mercenary and Dissident seems fitting.
I'd go for skills like Athletics, Stealth, Lore and Mechanics.
