Here are the edges and hindrances I have picked.
Edges:
Arcane Background (tribal medicine/shaman)
Linguist
hindrances:
Major: old ways oath
Minor: vow (revenge mother)
Minor: delusional (about danonites)
Um...Linguist isn't an Edge in Deadlands, it's in Rippers. It could probably be adapted, but it would probably be under-powered with languages coming up very seldom.
As for picking them skills/attributes:
All attributes are important for something. In more modern settings Strength becomes less important (as compared to a fantasy setting where strength is very important), Westerns are a bit in between. Guns rule the day in combat mostly, so strength is generally less important there (although melee combat is pretty viable). But don't be surprised when the cowboys in the saloon make fun of your scrawny character. And don't expect to be very effective in the bar-fight that's likely to break out after some unkind words are spoken.
But, if you want to excel at something, you have to accept some weaknesses. So, you'll just have to decide where your character is weakest.
Agility: is tied to several skills, including most combat skills. It's also used for agility tricks, and for resisting agility tricks. (Tricks are the miscellaneous things that happen in combat which aren't direct attacks...things like throwing sand in someone's eyes, or giving them a swift kick to knock them off balance).
Smarts: is tied to several skills, mostly non-combat. It can be used for Smarts tricks, and is used to resist Smarts tricks and Taunt tests of will. (Smarts Tricks are just like agility tricks except using brain instead of aim. Saying "lookout behind you!" for example, maybe flashing a light in their eyes.)
Spirit: tied to a few key skills (including Tribal Medicine and Guts). Used to recover from being Shaken (a situation where you can't act on your turn due to taking damage or being tricked/taunted/intimidated, and are more easily damaged). Used to resist Intimidate.
Strength: used to determine melee damage. Necessary for certain unwieldy weapons (gatling shotguns for example). Determines carrying capacity. May be necessary for certain challenges (moving a heavy rock, breaking down a door, those kinds of things).
Vigor: used to determine how easy you are to hurt. Also used to resist disease, poison, etc. Used to "soak" damage (you spend a benny to try to cancel wounds).
Skills (I probably should have mentioned this before somewhere): You have 15 skill points, it costs 1 point to raise a skill up to the linked attribute, 2 to raise it past the linked attribute.
-You should probably have some combat skill (Fighting or Shooting or both)
-Notice is important, it's used to spot things, and as anyone who's played an RPG can tell you, you're frequently checking if you spotted something.
-Guts is generally important, I generally recommend people take at least a d4. (You don't want to run scared the first time you run into a true "horror".)
-Healing is good for someone to have, usually good for 2 people to have in case the "healer" gets hurt.
Other than that, everything falls under the jurisdiction of whatever makes sense for the character. For an assassin-type character:
stealth is important. Fighting/Shooting. Athletics (for climbing into high places and the general assassins don't just walk around but go through difficult passages). Notice so that you can spot a target. Potentially Survival/Tracking to find targets and live off the land. And Streetwise for the social side of things.
And then as a shaman, you'll need Tribal Medicine. Survival/Tracking are also good here just for the living-off-the-land side of things.
Knowledges are skills. It's just an umbrella of several skills which all work the same way. (i.e. you roll it to see if your character knows something).