PHB Only Rogue with 32 Buy:
There are two broad types of rogue, and they are not mutually exclusive.
1) Trap Monkey
These are skilled builds. The only two skills that are mandatory are maxed out Search and Disable Device with the trapfinding ability. Every party needs one member with one level of rogue -- the skills can be kept maxed out cross-class if necessary.
Subsets of this include the "face" (social skills) and "scout" (hide/MS/Spot/Listen -- although magic is often better for divining than you will be!).
2) Dual-Wielder
This build is simply a combat style, using the rogue's abilities to deal damage.
For the former, all you need is one level of rogue. From there, build whatever you want on top. Rogue 1/Cloistered Cleric 19, Rogue 1/Druid, Rogue 1/Wizard, whatever. Just make sure your int is high enough to keep Search and Disable device maxed. Being a human is an obvious advantage for the bonus SP. Any combat style is appropriate; due to multiclassing your SA dice may be low, so something like Spring Attack could keep you safer.
For the latter, you are simply utilizing a combat style to do damage. In this regard, you are no different or more essential than the barbarian with power attack or the archer with his bow. In fact, you are less essential as sneak attack is often foiled by special protections.
To build a strong dual-wielder, you want to add as much bonus damage as possible to each hand. Sources of bonus damage in core only include: Rogue Sneak Attack, Bard Inspire Courage, Cleric Divine Favor, Ranger Favored Enemy, Horizonwalker Terrain Mastery, Fighter Weapon Spec, Magic Weapons (especially +1d6 elemental damage ones).
I would suggest, for a character working from level 1 on up, to open with something like this:
1 - Rogue 1 - Iron Will
2 - Ranger 1 - Track, Favored Enemy
3 - Ranger 2 - Weapon Finesse, Combat Style (TWF)
From there, you can do a two level fighter dip for more feats (especially Weapon Focus: Short Sword), go up to Rogue 4+ for more skills, SA, evasion, and uncanny dodge, or up to Ranger 6 for ITWF, a companion (meh), and spells.
I suggest Iron Will at level 1 because your Will Save will be terrible. Wisdom is a dump stat for you and your multiclassing will likely all feature poor Will Saves. Furthermore, feats that you really want (WFocus - Short Sword and Weapon Finesse have a BAB requirement). You'll get TWF for free. So you might as well knock out Iron Will early on. Combat Expertise is an option if you want the AC bonus, but I think the bonus to AC with 5 ranks in tumble and fighting defensively is sufficient, myself; Combat Expertise is only slightly more efficient, and you can't even use it until level 2.
I suggest the Ranger levels because they keep your skill points high, allow you to diversify your abilities (you're the trap man, the social monkey, the scout, AND the tracker, along with having a few useful Knowledge skills), give your BAB a boost, help out HP a bit, add CLW to your class spell list for wand use, and give you free TWF. Most importantly, Favored Enemy is a huge help. I'd select something that is immune to Sneak Attacks so that you won't be useless in those encounters: Undead, constructs, outsiders, and elementals are all decent choices. Otherwise, take something very common (it will help your skills too) like Humans or Goblinoids.
Whatever you do, do NOT build a TWF that uses Improved Feint. Improved Feint precludes you from full attacking. To TWF, you need to full attack. Thus, it is useless.
Ability scores:
STR - 10
DEX - 14
CON - 14 (You are in melee -- you need HP)
INT - 14 (You're a skill monkey)
WIS - 10
CHA - 8
That's 22 points. From there, it depends on your focus. For a social rogue, boost CHA. Otherwise you can dump it to 8. For a combat rogue, I'd bump Dex up to 15 or 16 and then put extra points into STR (DEX = To hit, AC; STR = damage, carrying capacity). For a scout rogue, I'd shoot WIS up to 14 (for Will saves and Spot/Listen) and boost Dex as high as I could.
Drop all stat bumps every 4th level into DEX, of course.
