That's how it goes, keep your head up and battle on. Those potions are used when opening card packs, you'll want to have 5 legendary and 5 alchemy potions per card pack, because one of each is used per card in the pack. Hopefully you can put those pots to use on some Chaos Legion packs here soon.

Keep up the good fight, don't get discouraged when you lose, and most of all have fun!