Cămașa pe care Andrei o cumpără nu este destul de ieftină, dar el este întotdeauna fericit.

In Romanian relative clauses for direct objects you typically use two elements:

• pe before the relative pronoun care (literally “that/which”)
• a resumptive clitic pronoun (o, referring back to cămașa) immediately before the verb

So pe care introduces “that/which,” and o “resumes” the object inside the clause. Together pe care o cumpără literally means “that which he buys.” The preposition pe marks it as a direct object, and the clitic o is required to keep the sentence grammatically correct in a relative clause.

destul de + adjective means “enough/quite” or “sufficiently.”

• este destul de ieftină = “it is quite/fairly cheap.”
• nu este destul de ieftină = “it is not cheap enough.”

Here destul de is an adverbial phrase modifying the adjective. Note that nu negates the verb este, so nu este destul de ieftină correctly means “it is not cheap enough.”

Romanian verbs are conjugated to show the subject, so subject pronouns are optional.

• dar este întotdeauna fericit is grammatically correct and understood as “but [he] is always happy.”
• Adding el clarifies or emphasizes the subject (Andrei), and can signal contrast: “but he (Andrei) is always happy.”

You can drop el in casual speech, but include it if you want extra clarity or emphasis.

As an adverb of frequency, întotdeauna normally goes close to the verb it modifies:

• el este întotdeauna fericit (most natural)

You can also front it for emphasis:

• Întotdeauna, el este fericit

Or place it after the adjective for stylistic effect (less common):

• el este fericit întotdeauna

Yes. In informal spoken Romanian:

• e is the contracted form of este.
• Subject pronouns like el can be dropped when they’re clear from context.

So nu e destul de ieftină, dar e întotdeauna fericit is perfectly natural in conversation. In formal writing you’ll often use the full form este and may include el for clarity or emphasis.