First Priority: Main DPS Spirit
Early on, focus on your starter spirit (Firespark, Aquablue, or Meowmew). Invest all rare resources into it — training fruits, EV fruits, star-up materials, etc. Only consider training a second spirit once your main can comfortably clear content. Check detailed stats and skills for any spirit in the Spirit Pokédex.
Second Priority: Key Support Spirits
Recommended: Dimo (given during main quest, significantly buffed) and high-aptitude spirits caught from the Pokédex. Don't spread resources evenly — only train the top one or two, and release the rest for materials.
Third Priority: Utility Spirits
Gentlechick, Duckjiji, Sonicdog, and other exploration essentials. They may not be combat powerhouses, but they multiply your adventure efficiency.
Tips to Avoid Pitfalls
Don't train every cool-looking spirit you find. Spend resources where they matter most. Star-up materials are especially precious early on — save them for your main spirits. Regularly clean your storage and release low-aptitude duplicates for materials.