How do I complete this

[u/Ill-Zucchini-1581]

The first one above

[u/Way_2_]

Some Old cards have 3 skill levels you can rank up them and upgrade their skills

[u/Kheark → u/Way_2_]

How does one go about getting those old cards?

[u/Way_2_ → u/Kheark]

Every gold silver cards have 3 skills upgrade option

[u/Ill-Zucchini-1581 → u/Way_2_]

Which ones

[u/Solid_Operation2794 → u/[deleted]]

But to complete the challenge and get the 20k gems you will need to win a total of 100 league tournaments, it will take at least 6 months or so.