Learn Turkish: Bu mücevheri alanlar, yatırım açısından şanslı olacak. - Those who buy this jewel will be lucky in terms of investment.

The word açısından (in terms of) works by forming a standard noun compound with the word before it. It literally translates to "from the angle of". Just like "elma suyu" (apple juice), "yatırım açısı" (investment angle) uses a bare noun first. Adding the ablative suffix to the compound gives us yatırım açısından (from the perspective of investment).

Could I use bakımından instead of açısından in this sentence?

Yes, they are completely interchangeable here. Both yatırım bakımından and yatırım açısından translate to "in terms of investment." While açı literally means "angle" and bakım relates to "looking/viewing", they function exactly the same way to express a standpoint or perspective.

How does alanlar translate to "those who buy"?

The suffix -an/-en creates a subject relative clause (who/which/that does). Here, the verb almak (to buy) becomes alan (who buys). Because the noun it describes is omitted (instead of saying "alan kişiler" for "people who buy"), the participle acts as a noun itself. It directly takes the plural suffix -lar to mean "those who buy."

Why is mücevheri in the accusative case if it comes before a participle?