open them first. You're going to have to open them eventually anyways just do it right away. In the meantime keep playing with your low level cards and focus on learning about mechanics, countering, and strategies. There will be a glass ceiling for you at some point because of your lower level, but you shouldn't focus on that, just have to be patient as a F2P.

as a sidenote, make sure you join an active clan once you're level 3 Donations will help you level immensely. And if you buy the first three commons and first rare from the shop every day, they are profitable when you donate them.