Emily_Kielb Welcome to Webnovel!
You will have to unlock them to read further. However, you do not have to purchase coins, as from check-in, power stone vote, and energy stone vote, you can earn 3 fast passes a day. With fast passes, you can unlock a chapter regardless of length (the cost of chapters in coins correlates directly with the length, longer chapters = more coins to unlock). There are also occasionally limited free reading offers, so you'll have to keep an eye out for that.
Hope this helps, & happy reading!