Able Learner Races of Destiny
You have a great aptitude for learning.
Prerequisite: Human or doppelganger.
Benefit: All skill ranks cost 1 skill point for you to purchase, even if the skill is cross-class for you. The maximum number of ranks you can purchase in a cross-class skill remains the same.
Special: This feat may only be taken at 1st level.
Jack Of All Trades Complete Adventurer
Prerequisite: Int 13.
Benefit: You can use any skill as if you had 1/2 rank in that skill. This benefit allows you to attempt checks (and take 10) with skills that normally don't allow untrained skill checks (Decipher Script, Disable Device, Handle Animal, Knowledge, Open Lock, Profession, Sleight of Hand, Speak Language, Spellcraft, Tumble, and Use Magic Device).
If a skill doesn't allow skill checks (such as Speak Language), this feat has no effect.
(This feat lets you take 10 in any profession or craft, knowledge, or under certain circumstance perform.)
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If you go int rogue you will accumulate approximately 268 skill points. Make note of which ones you can take 10 in, and which ones you can't.
Go over the skill list and try to limit yourself to 22 (or less) skills. Choose 3 skills to max, and 5 to near max(18) =159. Choose 5 to give only 5 ranks to for synergy (craft, jump, survival, use rope) = 13/184. You now have 84 points left for 9 skills = 9average, to play with.
NOTE: with synergies and ability bonus your scores will be higher.
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APPRAISE, int: Not bad in this world. DC 12 for mundane items and 15-20(+) for rare, so with your +3 int bonus @12th level you could have 18 points know the price of everything.
BLUFF, cha: I would. For one, most classes don't even have sense motive. Secondly, they won't have skill points. The only thing in this game better than diplomacy is the ability to lie about it. Since you won't have to lie often you won't need to max it.
DIPLOMACY, cha: Max it.
DISABLE DEVICE, int: Could come in handy, non magical devices have a cap of about 25, so you could conceivably master all the worlds devices. I wouldn't max it, but you might second rank it.
Escape Artist, dex: I would skip it. Don't get caught, and if you do, talk your way out of it.
Forgery, int: Forgery is capped by the opposed forgery check. I use it for my own aliases, and therefor no forgery check is opposed. It's tricky, and hard to get out of if the authorities catch you.
GATHER INFO, cha: You're going to need it, and you don't want to only get it from the bard do you? I would give it 18 ranks.
HANDLE ANIMAL, cha: I like the ideas above, but probably 10 is most of what you'll need (unless you make it a character trait/campaign driver).
HEAL, wis: Consider giving this some priority in a non magic campaign.
Intimidate, cha: I usually don't. Diplo and gather info and sense motive are more my style.
Knowledge, int: Without Knowledge Devotion this might just be enough to take Jack of all Trades and be able to take 10+ Int mod at all Knowledge.
LISTEN, wis: Personally i would give nearly 18 points to both listen and spot. There's a feat in CA (Quick Recon) that gives a free action Listen and Spot every round, and also a +2 Initiative. You might like it.
Move Silently, dex: Tempting. Depends on the direction of your character.
OPEN LOCK, dex: You can't talk a lock into opening. Lot's of good stuff behind locks.
Perform, cha: A few points in different performs might help your disguises, and love life. Probably won't be able to afford much.
Profession, wis: Remember that Jack of all Trades will let you take 10 at any profession check (sailor, cowboy, carpenter, astrologer, lawyer, architect, engineer), so if you take it, you won't need points here, but you can role play all day with few penalties.
SEARCH, int: Search is slower, and you can take 10, so you shouldn't need more than 10 points for mundane searches.
SENSE MOTIVE, wis: One of my big ones.
SLEIGHT OF HAND, dex: Unless you are building a thief i would only give it a second priority.
Spellcraft, int: If you don't have much magic perhaps take 10 is all you'll need.
SPOT, wis: Again, this is one of my big ones. Spot can make profit. Spot as a free action is easy profit and safety rolled into one.
Survival, wis: I would only take 5, i find the DM railroads me to where ever he wants me. .. .
TUMBLE, dex: Great skill, if you have the points. You should probably take 5 as it gives two synergies. More is better.
UMD, cha: When your DM finally starts breaking out the magic, guess who will have max ranks?
USE ROPE, dex: It will assist with climbs, escapes (if needed), survival situations, animals, captives, traps. . . don't leave home without it.
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As far as training, run mock battles against your allies for non lethal damage and it will be fun.
And of course, let's not forget the martial rogue, who get's feats as a fighter in exchange for sneak attack. Wrestle your DM into letting you take either feats or SA as you choose and he'll be sorry.
If you take this sort of build in a low magic campaign where the dm hands out magic items for plot, you will always have something to do in a round. Disguise and Sense/Diplo will likely be all powerful.
Oh, and don't forget to plan for the Leadership feat. Maybe a dip for a familiar and detect evil?