If you're trying to avoid combat and thus DT isn't that important to you, you can't go wrong with a classic suit. If you don't intend to be shooting very often, I'd actually recommend tagging Sneak instead of Guns so you can tip-toe past the situations you can, and save your heat for someone who's unavoidable.
As for weapons, I always pictured the suave, pistol packing speech-shark to carry semi-automatic pistols. If you have Honest Hearts you're in luck, since the .45 Auto combines class, style, and power all in one tidy package.
For my "talky" characters, I tend to grab both Black Widow / Lady Killer and Confirmed Bachelor / Cherchez le Femme, since you figure someone trying to talk their way through any situation wouldn't mind putting on a more flirtateous, sixual disposition to get what they want (especially since you never actually have to follow through), plus you'll get +10% damage to men and women.
If you go for semi-automatic pistols, the Grunt perk will boost 9mm's and the .45. Combat isn't always avoidable so it might be worth the perk point for the instant 25% damage increase. Things like Good Natured and Skilled work well for traits if you're going to stick to one weapon type, you get a pretty massive speech score early on by combining them.
If you end up going the sneak attack route, The Professional increases the damage you do on sneak attack crits for pistols.
I'd have more ideas but my brain is working kind of slow at the moment.
There aren't really a lot of speech related perks outside of BW/LK and CB/CF, so you can kind of pick according to what you end up doing more often in your playthrough.