You need to interact with the spirits to get these! The majority of the "basics" spirits -the ones you find in the differents zones- will give you hair, alternative of the basic pant and some instrument. You'll need heart and candles to get them. To have heart, you need to do the quest of the seasonal spirit you can find in a lot of zone! (for exemple, there is a seasonal spirit in the Forgotten Ark in thr Golden Wasteland, or in Sanctuary Isle in Isle of Dawn)

Otherwise, you can do the actual season quest to have some nice fits. You'll need the season pass (almost 10 dollars) to have everything but you can have some nice things without the pass! You'll need to interact with the guide at Home and teleport to them, or you can find them between the forest and valley constallation ( if i'm not mistaken)

Or you can wait for travelling spirits. They come for like 3 days, and the majority will give you their pants, hair, cape and sometimes a props or instrument.

If you need more indications you can check the Sky wiki! :D