When it comes to activewear, leggings and yoga pants are consistently among the most profitable items. Gym clothing such as tank tops, shorts, and other workout clothes are also popular and can bring good revenue. Additionally, athleisure and versatile pieces like sports bras and performance jackets have become increasingly popular for daily wear. A good way to know about new trends and what's selling well is to keep an eye on fashion and lifestyle trends and research similar brands in the market.