zhèyàng zuò gèng hǎo.

It’s not missing anything. 这样做 (“doing it this way”) functions as the subject, and 更好 (“is better”) is the predicate. So the structure is: [这样做] [更好] → “Doing it this way is better.” You can make the subject explicit if you want:

• 我们这样做更好。 “It’s better if we do it this way.”
• 你这样做更好。 “It’s better if you do it this way.”

• 这样: “like this/this way,” neutral and common.
• 这么: very colloquial; with verbs it overlaps 这样 (e.g., 这么做 = 这样做). With adjectives it often means “so/this (degree)” (e.g., 这么好 = “so good”).
• 那样/那么: “like that/that (degree).”

Notes:

• 这样做更好 / 这么做更好 are both natural.
• 这么好 means “so good,” while 这样好 often means “it’s good if we do it like this” (proposal/acceptance), not “so good.”

更 marks a higher degree relative to some reference, which can be implicit from context. You don’t need 比. If you want to be explicit:

• 这样做比那样好。 “Doing it this way is better than doing it that way.” You can also say A比B更好 (with 更 for extra emphasis) or simply A比B好.

In this sentence it’s most natural to view 这样做 as the subject (“Doing it this way”). If you add an explicit subject, 这样 becomes an adverbial modifier of the verb:

• 你这样做更好。 “It’s better if you do it this way.”

Pronunciation: zhè yàng zuò gèng hǎo (4–4–4–4–3).

• 更 is pronounced gèng (fourth tone) when it means “more/even more.”
• There’s no special sandhi among the four fourth tones here; 好 is third tone and, at sentence end, stays as a (often half) third tone.

Yes:

• 这样子做 is acceptable (often more colloquial/regional).
• 照这样做 / 按这样做 mean “do it according to this (way).”
• More formal alternatives: 用这种方式做 / 以这种方式做.

Try:

• 这样做更好吧。 (adding 吧 softens it)
• 这样做会更好。 (predictive/hedging)
• 我觉得这样做更好。 (opinion marker)
• 还是这样做更好。 (preferential suggestion) You can also hedge with 可能/也许: 这样做可能更好。

Yes: 更好地 + Verb modifies how the action is carried out (“to do X better”).

• 为了更好地完成任务，我们… “In order to complete the task better, we…” Compare:
• 这样做更好。 “Doing it this way is better.” (evaluation of method)
• 更好地做这件事。 “Do this thing in a better way.” (adverbial modification)

Use 最:

• 这样做最好。 “Doing it this way is best.” Also note 最好 + VP often works like “you’d better…”:
• 你最好这样做。 “You’d better do it this way.”

Use 不如 or 没有…好:

• 这样做不如那样好。
• 这样做没有那样好。

Yes:

• Intensify/hedge: 更好一点(儿) / 更好一些 (“a bit better”).
• More emphatic: 更加 (often with disyllabic adjectives): 这样做更加清楚。
• More formal: 更为: 这样做更为妥当。
• Softer/less absolute: 比较好: 这样做比较好。

Absolutely, to be more precise:

• 这样做更合适/更方便/更安全/更有效/更合理/更妥当/更可取。 Pick the adjective that matches what you mean by “better.”