Yes, aloe vera can be used as a serum, particularly for hydration and soothing irritated skin. It's lightweight and can be layered under other moisturizers or used alone, especially for oily or acne-prone skin.

Aloe vera and retinol serve different purposes. Aloe vera is primarily for hydration and soothing, while retinol is for anti-aging and skin cell turnover. One is not inherently 'better' than the other; they address different skin concerns and can even be used in conjunction with each other, carefully.

The 'No. 1' face serum is subjective and depends on individual skin needs and preferences. Popular and effective serums often contain ingredients like hyaluronic acid for hydration, vitamin C for brightening, or niacinamide for calming and pore refining. Consider your skin type and desired benefits when choosing a serum.

Applying aloe vera gel to your face nightly can provide hydration, reduce inflammation, and soothe minor irritations. However, some individuals may experience dryness or irritation with frequent use, so it's important to monitor your skin's reaction and adjust usage accordingly.