I've had a lot of experience with thieves, having played all of them multiple times except for poisoners (which have never appealed to me).

You can take one full path and a few general skills and be very viable. There's no need to rely on Devious Versatility edge(s) to make you do well. It all depends on your knowledge level and what kind of circumstances you will fight in.

City Slickers do well alone or in cabals. They aren't great at killing, but are great at surviving and hoarding shinies.

Binders do well if they are in circumstances where they can fight their targets alone. Cabal warfare, shifters, and outlanders in particular make many of their advantages disappear.

Thugs can do well in many circumstances, as pure combat is always useful.

Trappers and poisoners are a huge investment in time and energy, and I will refer you to earlier discussions on their viability.

Climb is useful for ragers who can't use flight potions. For everybody else, there's better skills.

Gentle Walk should be mandatory for all thieves. It's just that good.

Shield Block is good if you tank a lot (as a non-felar). You can get some ranking mileage from it, and it helps if you only intend to knock out and rob your foes, but it will be very limited if you actually intend to kill another player. Your only saving grace as a thief is doing as much damage as possible before your target escapes, shields will only make that impossible.

Blackjack, garrotte, and weapon butt blackjack all have different strengths and weaknesses. Blackjack has some of the most noticeable advantages in success rate, so it's not uncommon to take it even when you already have another knockout skill. If you are wanting to knock people out as a gnome, be prepared either to learn traps/poisons or become familiar with cheap enlarge preps.

Discerning gaze hides the room echo people get when you look at them from the shadows. And it's nice, but not critical unless you are scoping out somebody who is likely to let loose some area damage to flush you out.

Improved hide, has some uses but can be skipped without any regrets.

The locksmithing path is rather niche and can be skipped.

There's some good skills in the Mystic path, scrolls should be a high priority for any non-rager thief. The other mystic skills are less critical. There's just too many buffs and maledictions in scrolls you can pick up easily which will swing a fight heavily into your favor.

My advice is to search the PBFs of past thieves to see what combos they have worked with and what edges they took, and you will get a decent idea of what is possible. I would also suggest just playing whatever sounds good and using that experience for future characters.