Need ingage? Use Hook. Need more? Buy
or
or BOTH!
Taking too much damage? Flaw away. Not enough? Defensive hook. Not enough? Lantern has a sheild. Not enough? Use
or 
Not doing enough damage? Your "ranged" auto attacks will deal a ton of damage! You will also get free AP to do more damage on your spells that are already have high damage for a support!
Still taking too much damage? You get free armor with your ap souls too.
Need a gank? Lantern
Team mate dying? Lantern
Need vision now? Lantern
Too risky to get souls? Lantern
Hooked your enemy but its likely they can dash away? Press R and watch as they arent able to run away at all!
Thresh has fucking everything the kit and tools for any situation. Honestly no reason not to play him other that you can't heal like nami or soraka