Can I only get a full Collection by luck? What is Trade-up?
You can – if you are lucky and buy enough packs – hope to get a full Collection by pure luck.
But there is also a trade up function where you can trade-in a number of Artifacts of one tier for one Artifact of the next tier. Basically a combination of luck, trade ups and a soon to come marketplace will allow you to further complete your Collections in many ways.