Creating a psy using marksmen

[Agumaru]

how would I make a build focused on using psy while being good at shooting things with the occasional grenade

[TheAverageGortsby]

Focus on psi is exclusive to all other combat disciplines except perhaps throwing which requires relatively small investment compared to guns/xbow/melee, because the stats that make psi good provide no benefit to guns, and vice versa.  If you truly mean to focus on psi, then you won't have enough stat points to get good also at shooting.  If you want to use psi, your guns will be disappointingly poor and you'll stop using them, making your build a waste.  If you want to use guns, you can still use psi quite effectively, but I wouldn't call it a focus on psi.  It'd be a focus on guns with strong psi support.

If you want to do this, you'll need to use ARs, sniper rifles, or shotguns.  You simply won't be able to spare the points to get enough Dexterity to use SMGs or energy/chem/gunpowder pistols.

So, now you should be able to plan well enough that you can go look through the existing guides on the forum here and find some good ideas.  As long as you're not playing on DOMINATING, you can make do with 12 Will + 6 Intelligence for psi and 10 Perception + 5/6 Strength for ARs/shotguns.

There are plenty of hybrid build guides on the forums to get you rolling.

[Sykar]

how would I make a build focused on using psy while being good at shooting things with the occasional grenade

PSI Sniper works fairly well. Don't listen to the dogma that Guns offer nothing for PSI. Especially early game you will be constantly dry so being able to fill in Aimed Shots and opening with Snipe gives huge benefits. What glues PSI with other disciplines well together is Premeditation. Thanks to that talent for example it is possible as a Sniper with a Rapid Spearhead rifle to open with Snipe -> Aimed Shot -> Premeditation+LoC+Berserk to CC the rest of the enemies. There are a couple of other combos like using the Cryo Induction feat, open up with Snipe -> Premed+Crystasis-> Aimed Shot. That combo is strong against super high health targets like you meet in the arena. Another strong combo is Premed+Thermo Destabilzation-> Aimed Shot against larger groups.
You will end up with something around 12 perception and 12 will compared to 16 for a pure builds repsectively, but it is not nearly as much of a difference as it seems. Snipe and Aimed Shot are prone to deal too much damage in the first place so losing around 10%-15% damage is rarely if ever a concern. PSI is very powerful and never misses, though certain CC effects can be resisted of the TC school. Note that some stuns are irrestiable regardless of skill level. The Electrokinetic Imprint for example will never be resisted and is especially strong against robotic enemies.