Learn Italian: Se avessi i soldi, compreresti ciò che ami? - If you had the money, would you buy what you love?

The imperfect subjunctive forms for io and tu are identical for all verbs, including avessi (from avere). We know it means "if you had" because the second half of the sentence uses compreresti (would you buy). If the subject were meant to change from "I" to "you", an Italian speaker would likely add the pronoun to the first part to avoid confusion: Se io avessi i soldi.... Since there's no pronoun here, we assume the subject "tu" is the same for both verbs.

Why do we use ciò che instead of just cosa to translate "what"?

In English, "what" does double duty as a question word and as a phrase meaning "that which" or "the things that". In Italian, you use cosa (or che cosa) for questions. When you mean "the things that", you must use a relative pronoun like ciò che. Since this sentence translates to "would you buy the things that you love", ciò che is the correct choice.

Can I use quello che instead of ciò che in this sentence?

Yes, absolutely! Quello che and ciò che mean exactly the same thing and are completely interchangeable. You could easily say ...compreresti quello che ami? and the meaning wouldn't change at all. Ciò che is just a tiny bit more formal and elegant, while quello che is slightly more common in everyday spoken Italian.