As a psiker you don't need DEX/STR/PER.
First you need to decide if you want Psychosis or Tranquility.
AGI should be 10 if you want Blitz or 6 if you want Sprint or 3 if you decide this is your dump stat (not recommended).
CON should be 10 if you want Thick Skull (why? Locus of Control is loads better), 9 if you want survival instinct (for Psychosis crit combo), 7 if you want Stoicism, 5 if you want Conditioning, 3 if dump stat.
INT should be 7 if you want Skinner/Power Management/Clothier, if you have spare ability points this could be as high as 8.
WIL should never be lower than 10, 15~16 is a good number.
I would recommend full dodge, evasion, and stealth for Tranquility psi because you want the full hp AP reduction bonus for as long as possible. Psychosis psi is a different story - your play style will determine your skill investments.
Armor - I think the best armor would be a psi beetle carapace tactical vest for the psi bonus and psi cost reduction. Alternatively a high CON psiker can use infused pig leather armor + infused pig leather tabi. Infused Ancient rathound leather armor/psi beetle carapace riot gear are also viable (but imho less effective)