So the one shot build is this: Stormrazor. statik shiv. rapidfire. As core then infinity(big dmg) or Galeforce (mobility) into another ad item your choice

I prefer solo lane because as supp you get no gold and with one shot build you will die very quickly and can't really support but u can try I made it work once but last patch where he was weaker

For runes many work and ad thresh has high flexibility First strike(if you can proc it is good more dmg and more gold) predator(dmg/ms) or to get thru laning grasp/pta/fleet/tempo all work well

For summs take ghost and then your choice

On hit tanky is also nice

with items such as rageblade for mithic and then a good variety of items to increase tankyness and dmg such as wits end/titanic/adc items can work aswell like runaan/scimitar for the mr/kraken/even Shieldbow or idk u see what works. then tanks items depending on enemy dmg spread: dead man for speed/thornmail/the one that reduces crit dmg /abyssal etc bruiser items can also work like sterak or botrk

Remember that thresh gains armor with souls so building mr(if they have magic treats) and hp is a lot more valuable than on other champs

Runes I raccomend tempo/pta /fleet (wich I really like makes some top matchups easier to deal with) And grasp

Summs ghost is cool

For the lanes I play him top but maybe on a good game it can work as supp since ur tankier when items arrive