Leadership is best on casters, because they don't get value out of the damage boost from Leadership, since it only affects attacks with your weapon (unless you really want to boost staff of magus).
Skip the weapon talents (bow, 1handed,...) altogether, because you can use Tenebrium weapons (either Tenebrium bows or any bow that your crafter has enchanted with Tenebrium) later, which check your Tenebrium skill and not your bow skill.
Charisma is something that you can just as well cover with your gear.
You can skip Pickpocket, because you will always have more than enough Gold. However if you like stealing stuff use 1 point in Scoundrel so that you are able to pick the skill "Walk in Shadows", which turns you invisible for a few turns.
So just put Marksman at level 2, 1 in Scoundrel and the last one to either boost your saving throws or Geo/Witchcraft if you plan on giving your Archer some buffs.
