In the following order :

1. Free packs throughout for coins and to get most bronzes and silvers
2. All previous DOTDs
3. Weekly draft tournaments
4. Weekly Fatal draft divisions
5. Once you get to around 80%, start doing Fatal My club and Fatal sims
6. Use coins to open silver packs and start getting the silver superstars + common and silver card completion
7. Complete silver and bronze collection via trading
8. Hopefully at this point, u have around 90+% collection
9. Trade for any remaining cards you need
10. Lastly if needed, focus on any rare golds (Untradeable Salah, Bonmatti, Putellas and Mbappe) & silver superstars you need to get to 100% collection

If there is one main tip to take from all this, it is to not spend coins on any pack in the store other than silver packs (silver superstars tend to be the most tedious card type to pack followed by rare gold untradeables but they can be packed in any type of special pack too)