Ashley did nothing wrong.

Glowing Up / Styling Competitions: Don't need to glow up/upgrade pieces with subtags. I wasted a lot of shiny bubbles on pieces I did not need. Focus on upgrading 5 main tags (Sweet, Sexy, Fresh, Cool, Elegant) and you can still get Perfects in competitions and re-use the same outfits. I also wish I took my time and planned out which pieces in each of the 5 main tags to craft/pull for and invest in.

Upgrade Skills / Heart of Infinity: I wish I had upgraded foraging, bug catching, grooming, and fishing sooner so I could collect more materials while exploring and progressing the main story. This is easily achievable using Realm of Nourishment, and trust me you will need these skills maxed out...

Use Energy: Related to the above, use that energy wisely as it replenishes slowly! You can use it at the different realms for leveling up skills and getting Eurekas, Shiny Bubbles for improving styling points and materials for crafting quest outfits (Miracle outfit).

Collect Fragrances / Heart of Infinity: Whilst not needed these are super nice to have to help with purifying Esselings, and you can find lots of Whimstars, Chests, and Dews on the way!

Mark Dews: You can use interactive maps such as https://infinity-nikki.interactivemap.app/ and https://mapgenie.io/infinity-nikki/maps/miraland to track which dews you've already collected. This can help if you want to keep unlocking outfits with Kilo! (Note that some of these maps might be incomplete as the game is still new)

Eurekas: You do not need to upgrade every type of Eureka you get--this chart for Eurekas can help with prioritizing upgrades. Also, it randomly chooses a color when you level it to 10, you can't change it but you can get the same one and upgrade it with the same or different level 10 one to try for a new random color.

Rong Hua - flower hairpin

Tuan Shan - hand fan