I found my Woodelf wis/dex land druid with Guild Artisan background (Insight and Persuasion) did pretty well on speech checks--and checks overall. Larian does a fairly good job of providing alternative routes to passing them (e.g. a wisdom option as well as a persuade option), plus you can fairly easily boost stats with Guidance. I think it's good to have a high-Charisma trader character, particularly if you're playing a character who doesn't steal and is inclined to notice what companions are up to, but that needn't be the PC.
