Cho'Gath Runes explained
There's one set of runes for Cho'Gath on patch
11.8
that is the clear favorite for LoL players and pros alike. The best Cho'Gath Runes on the position 
Top are Resolve as the primary path and
Inspiration as the secondary path with a pick rate of 61%. Besides runes you should take a look on Cho'Gath Build and if you are interested in pro matches take a look at Cho'Gath Probuilds. If you want to discuss
Cho'Gath then you should visit the champion subreddit.
Primary path on Cho'Gath
Resolve empowers the survivability of Cho'Gath and increases the tankiness. Most of high elo players – and our LoL pros in the the major regions – have agreed that
Grasp of the Undying is the best keystone rune to run on
Cho'Gath. This keystone rune gives Cho'Gath alot of sustain and helps to force your opposing champion out of the lane. This is usually followed up by taking
Demolish,
Bone Plating and
Overgrowth.
Demolish increases your pressure on the enemy turrets. This rune will help you to punish bad roams or backtimings of your lane opponent.
Bone Plating make Cho'Gath overall tankier, by decreasing the amount of poke damage in the early game.
Overgrowth increases your maximum amount of health.
Secondary path on Cho'Gath
When it comes to your secondary path, most
Cho'Gath players prefer to go with
Inspiration.
Inspiration opens creative opportunities on Cho'Gath troughout the match. On the
Inspiration path, the best runes for Chogath are
Biscuit Delivery and
Approach Velocity.
Biscuit Delivery is a great rune for laning as it gives additional health and mana, which can help in more aggressive lanes. Cho'Gath gains bonus movement speed by
Approach Velocity, while moving toward enemy champions that are immobilized or slowed. This rune is perfect to follow up engages by your teammates.