Advice for supplements. Like guidance!

For a 31-year-old woman and would like guidance regarding supplements for general health maintenance. I am considering taking Omega-3 and Magnesium supplements to support overall health, stress management, and sleep quality. I would like to know: 1. Are Omega-3 and Magnesium supplements recommended for someone like me? 2. What dosage is generally suitable for long-term maintenance? 3. Which forms of Magnesium (e.g., glycinate, citrate, etc.) are preferred? 4. How should these supplements be taken (daily or on alternate days, with food or without food, morning or night)? 5. Are there any side effects or precautions I should be aware of? 6. Should I get any blood tests done before starting these supplements? Goal is to maintain a healthy body, support regular sleep, and address general nutritional needs rather than treat a specific medical condition.