Baseline build Stitches

Level 1:

Patchwork Creation   is the best choice here, giving you a good sustain healing as well as some armor. It's good in early game and late game.

Savor The Flavor   can be a good choice if you are willing to play the E build and want a strong presence in late game. Combined with other E talents it can be really good.

Level 4:

Tenderizer  is the best choice here. Slowing the enemy after a hook, giving you healing.

Level 7:

Serrated Edge is the best choice here. Reducing the cooldown of your main ability ( aka The Hook ), plus it does extra damage.

Second Helping is the go-to talent if you are playing the E build. Even if you lose the Loan bonus, it still gives you a second charge of Devour , works well with the level 16 talent Digestive Juices .

Level 10:

Here i'd say that both choices are viable, depending on your playstyle. Either you want to give your Hook   the best possible value then i'd pick Gorge or you want to be more efficient during teamfights then you should pick Putrid Bile . 

Level 13:

Meat Hook is the best choice here. It adds a really good amount of self healing whenever you hit with your Hook .

Chop Chop is also viable, especially against melee comps as it allows you to AA more often and increase the value of Tenderizer .

Level 16:

Pulverize is a good choice as it adds an AOE slow to your toolkit.

Digestive Juices is the best choice if you are playing the E build, otherwise I don't find it extremely strong if you only have 1 charge of Devour since it is a 20sec cooldown.

Level 20:

Master Hooker is the best choice here. One hook on the enemy carry can completely win the game, negate healing for 2sec is huge.