There are two types of light from the sun that cause sun damage - UVA and UVB. Your skin needs protection from both types to avoid premature ageing and skin cancer. SPF protects against UVB, so look for products with broad spectrum coverage as this will protect against both UVA and UVB.
SPF is a number that indicates how long the sun would take to damage your skin when using the product exactly as directed vs the amount of time with no sunscreen. Black skin is thought to naturally have an SPF of 13, which is a great start but it’s not enough to stay protected.
Everyone should ideally be wearing SPF 30 every day. Even if your makeup or skincare products contain SPF, this isn’t usually enough to keep your skin protected from both UVA and UVB. Your sunscreen should be applied directly to your face before the rest of your routine.