Basically title. Looking to build an archery ranger since our front lines is clogged with a magus, rogue, animal companion and melee druid, however I could easily go switch hitter. I've asked the DM but he's pretty tight lipped about what favorite enemy I could take. Starting level is 1, and I am all right with picking a less prominent favorite enemy at 1 since the next one I pick can be +4.
Human first. Then Undead. Then outsider (evil). You might make it to level 15, and if so, I really don't know what you should take.
You should probably look at the Urban ranger variant, of course.
You do meet some fey during the book, but its in the mid levels, and undead are more important at that time.
You'll be facing off against humans regularly through the entire book, so it should be your highest.
==Aelryinth
Have you checked out the Council of Thieves Player's Guide?
It's supposed to be spoiler-free, and lists the most common favored enemy types.
Not sure why your DM doesn't want your favored enemy to be useful.
Seconding Aelryinth. May also want to consider outsider (native) as well.