Because I can't help myself: Bilbo theme build. I would actually not do a rogue. That is what Gandalf sold him to the dwarves as, but not really his original skillset. He was actually more of a goofball that tried talking his way out of things in his younger years, then as time went on he was corrupted by the ring, so I would do a bard with a sprinkle of warlock near the end. He taunts and distracts enemies in a way that I would say fits with the Lore Bard's Cutting Words ability. (think about it as his taunts giving a penalty to Smaug being able to find him; in DnD that would be a perception check)
Also, the lore bard gets extra skills at level three, and I think that is when you pick up the more thiefy stuff as his adventure goes on and he becomes more competent.
Build:
Lightfoot Halfling
Hermit background - it comes with herbalism "toolkit" in the books
and he is a homebody.
Lore Bard
Str 8
Dex 16
Con 14
Int 10
Wis 10
Cha 16
Honestly his stats would be worse than that, but you may as well use what they give you.
Racial skills: Stealth
Hermit skills: 'Medicine' (hehe) and religion (which doesn't quite fit, but oh well)
1st Level Skills: Insight, Perception, and Persuasion/Deception (whichever you like more)
3rd Level skills: Acrobatics, Slight of Hand, and whichever of the Charisma one you didn't pick at 1st level
For spells, definitely pick up the Vicious Mockery cantrip at 1st level and probably Heroism for when he musters his courage. Invisibility at level 3 (and maybe detect thoughts since he is always listening in to conversations). Definitely Feign Death at 5th level. Other than those, I'd just pick up a couple damage dealing spells and whatever seems fun.
Taking some Warlock levels is optional to give it some flavor, but not needed. By the time you hit the higher levels you'll have a better idea of how you want to approach things, but a fiend or great old one would be good. And while I doubt they'll have it, the Pact of the Talisman would be a perfect fit as it could be the one ring
