WARNING WALL OF TEXT AHEAD
Sniper builds are my favourite so I can definitely help you with that.
There are many ways to build a sniper, but here are some general tips:
You should have 5 STR, that's enough to use all sniper rifles (except for one unique found near the end of the game that requires 6, but it's not worth it) or 6 if you plan on using assault rifles as your sidearm.
DEX is up to you. Snipers don't benefit from it per se, unless you want to have some DEX feats or use SMGs/pistols as your sidearm, avoid lockpickingg and throwing penalties etc. You can even dump it all the way to 3 if you plan on using ARs and odn't care about the skill penalties, leave it at 4 if you want to avoid penalties. I usually go with 7 because I like to use pistols as a sidearm.
AGI is pretty important beacuse snipers benefit a lot from being able to kite and many good feats require it. You could set it at 10 to get Blitz and all other cool AGI feats like Interloper, Escape Artis, Uncanny dodge etc. but I tend to set it to 6 to just get Sprint.
CON is up to you. You can dump it to 3 if you wish but to me it's just too low and doesn't allow much margin of error, I usually go with 5.
PER is your most important stat, missing hurts snipers the most. Try to get it as high as possible, it owuld be perfect to set it a 10 at character creation and put all level up points into it as well to get it 16. It's no big deal if you start with one or two points less though.
WILL is a dump stat, set it to 3. Maybe 4 if you don't want to get persuasion penalty, but you can use it effectively even with a penalty as long as you max it every level.
INT depends on how much you want to min-max. Get 7 if you want to get a crating feat that requires 7. Get 6 if if you want to get a crating feat that requires 6. 5 is a good number if you want to craft and save some skill points. 4 means no penlaties to crafting. You can craft with 3 too, but it's pretty tedious. I go with 5 if I don't want any crafting feats.
About feats:
Aimed Shot, Snipe, Critical Power and Sharpshooter are an absolute must. Playing a sniper is all about stacking critical damage/special attack bonuses and using it with Aimed Shot for a guranteed kill every 3 turns. Snipe should be used at the beginning of combat.
Depending on your sidearm of choice you will want different feats. If you want ARs get AR feats, if you want SMGs get some SMG feats etc. You will figure it out. I tend to go with pistols and take Gunslinger, Kneecap Shot, Point Shot and Rapid Fire.
Other feats that can be useful include Sprint, Paranoia (for the +5 initiative, I will talk about that later), Nimble, Interloper, Blitz, Uncanny Dodge, Recklessness, Ambush, Escape Artist etc. Basically anything that allows you to be more mobile and get out of harms way or hel you score critical hits.
About skills:
Max guns every level, that's pretty obvious.
Throwing is useful, 80 points sohuld be enough to hit at acceptable ranges.
Dodge/Evasion are "all or nothing" kind of deal, you need to keep them high and support them with feats/gear to make them truly shine. I usually don't find enough points to invest heavily into them, but it's up to you.
Max stealth, or at least keep it high. Snipe damage and Ambush crit chance scale with oyur stealth skill.
Hacking/lockpicking/pickpoceting is up to you.
Traps are useful, but not as useful as fro crossbow build. It pays off to get at least 40 though, to use crawler bear traps and some mines.
You will need mechanics to craft good sniper rifles and believe me yuo want to craft them. Try to keep it high so you end up with at least 100+ near the end of the game.
Electronics are incredibly useful for making goggles and adding smart modules to your guns. I would reccomend keeping it high as well, but it's not as crucial as mechanics. You need at least some points to add anatomically aware scopes.
Chemistry isn't all that useful, unless you want to use grenades/traps a lot. However, since I tend to use 9mm pistols as my sidearm, I get 35 vhemistry to craft acid bullets.
Biology is useful as hell, crafted drugs are powerful. Get 50 if you want to craft +15% crit chance drugs, 80 if you want pills that make you immune to stuns/incapacitation, ignore if you can't afford to spend so many points.
Tailoring is incredibly useful for crafting infused leather armors and tabi boots. I would reccomend keeping it high as well, but again it's up to you.
Persuasion/Intimidation/Mercantile I also leave to you. I like persuasion but it's personal preference.
About gear:
Your main weapon will be a sniper rifle (duh). At the beginning of the game try to get whatever you can, preferably with a normal scope and bipod.
Later, you will want to get a Reaper (+25% crit damage) with anatomicalyl aware scope (+50% crit damage) a bipod and a smart module.
As soon as you get a Spearhead frame and Rapid reloader is when the fun begins. Spearhead sniper with a rapid reloader costs only 24AP to shoot, meaning you can shoot it twice a turn. Add an anatomically-aware scope and a smart module and you are set for the rest of the game.
You absolutely need to wear night vision goggles, being able to ignore light penalties to hit is just too good. Preferably smart goggles to boost your damage even more, but this is your choice.
Armor is preference mostly. I tend to go with infused pig leather armor because it has high resistance and incredible health bonuses. Try to keep it light though.
As for the belt I tend to go with doctors pouch, makes it so all drugs cost only 2 AP to use, just enough to take a drug after shooting your Spearhead twice.
Infused siphoner tabis are probably the best boots you can wear since they make you immune to immobilization.
Shields are entirely different topic, I will just say I think efficent low frequency are the best you can craft.
Sidearms are also an entirely different topic. I will just say I prefer pistols because:
-they have no move/close combat/STR penalties, meaning they will be there to save you no matter how bad it is
-they can use Kneecap Shot
-neo lugers with laser sights get +15% precision, meaning they will hit even if you suffer some penalites to your hit chance
-they give +7 initiative with Gunslinger
Why do I care about initiative so much you ask? Because I tend to play perma-death and having high initiative saved my ass more than once when my stealth approach failed. Overall, ARs and SMGs will have waaaaay more DPS than pistols, but I don't see a sidearms as my DPS source- it's supposed to help me get out of sticky situations where I can't use my sniper. Yeah, ARs will deal a lot of damage, but when you get hit by crippling strike (and get a huge penalty to your hit chance because you don't met the STR requirement) they are not as useful anymore.
So yeah, I think I talked about everything there was to talk. Here is a link to the build I'm going to play when the expansion comes out:
http://underrail.info.tm/?build=AwGloJgVhGHYQDZYgIwwMwtRmibhhE4yrAQgAcqREoZCDIEALEhU4fbkfc81gygMyFqBYIWATlg0oWKAjgxKMqaiATook quick pockets at lvl 24 only because I run out of ideas what to get. Check huxkey/crafting bonuses.
