Non compro il sugo pronto; preferisco farlo in casa.

Italian often leaves out subject pronouns because the verb ending already shows who is doing the action.

• compro = I buy
• preferisco = I prefer

So io is not necessary here. You could add io for emphasis, especially if you are contrasting yourself with someone else, but the normal version is without it.

Italian usually makes a sentence negative by putting non directly before the verb.

• compro = I buy
• non compro = I do not buy / I don’t buy

This is much simpler than English, because you do not need an extra helping verb like do.

Italian uses the definite article much more often than English does. Even when speaking about something in a general or familiar way, Italian often keeps the article.

So:

• compro il sugo pronto literally looks like I buy the ready-made sauce
• but in natural English it is simply I buy ready-made sauce

This use of the article is very normal in Italian.

Sugo usually means a sauce, especially one associated with pasta or cooking juices.

In everyday Italian, sugo often suggests:

• pasta sauce
• tomato-based sauce
• a homemade cooking sauce

It is not always exactly the same as English sauce in every context, but here it is a very natural word.

In Italian, adjectives often come after the noun, especially when they describe a practical or concrete quality.

So:

• sugo pronto = ready-made sauce / ready-to-use sauce

Also, pronto here does not mean soon. It means ready or already prepared.

Adjectives in Italian must agree with the noun they describe.

• sugo is masculine singular
• so the adjective must also be masculine singular: pronto

If the noun were feminine singular, you would use pronta instead.

After preferisco, Italian can use an infinitive to say what the speaker prefers to do.

• preferisco = I prefer
• fare = to make / to do
• preferisco fare... = I prefer to make/do...

Here, farlo means to make it.

So the structure is:

• preferisco + infinitive
• preferisco farlo = I prefer to make it

When object pronouns are attached to an infinitive in Italian, they join onto the end of the infinitive.

With infinitives, the final -e usually drops:

• fare + lo → farlo
• comprare + lo → comprarlo
• prendere + la → prenderla

So farlo is the correct combined form meaning to make it.

Lo is a direct object pronoun meaning it, masculine singular.

Here it refers back to il sugo.

So:

• il sugo = the sauce
• farlo = to make it

It replaces the noun so you do not have to repeat il sugo.

Because the it belongs to the action to make it, not directly to I prefer it.

So the natural structure is:

• preferisco farlo = I prefer to make it

If you said lo preferisco, that would usually mean I prefer it, without the idea of making it. In this sentence, the pronoun is tied to the infinitive fare, so it becomes farlo.

Both a casa and in casa can relate to home, but they are not always identical.

In this sentence, in casa suggests at home / in the house / homemade, and it works very naturally with the idea of preparing food yourself.

• farlo in casa = make it at home / make it in-house / make it homemade

A casa is also very common for at home, but in casa often sounds especially natural when talking about something being made within the home.

Because in casa is a fixed everyday expression.

Italian has several common expressions with casa where no article is used:

• a casa = at home
• in casa = at home / in the house

If you were talking about a specific house as a physical building, you might use an article:

• nella casa = in the house

But here in casa is the normal idiomatic phrase.

They are both in the present indicative:

• compro = I buy
• preferisco = I prefer

The present tense is used here to talk about a general habit or usual preference, not just one specific moment.

So the sentence means something like:

• I don’t buy ready-made sauce; I prefer to make it at home
• in the sense of that’s what I normally do

The semicolon links two closely related complete ideas:

• Non compro il sugo pronto
• preferisco farlo in casa

It shows a stronger break than a comma, but a closer connection than a full stop. In English, you could also write this with a semicolon:

• I don’t buy ready-made sauce; I prefer to make it at home.

So it is mostly a punctuation choice that highlights the contrast between the two statements.