Gems

The main currencty in the game. Not to be confused with jewels.

Use for Costumes and inventory expansion to start. Full capacity on your main and ~240 on alts (for GotD) should do. After all costumes are collected you can try the Vending Machine and using them for traits on gear and, later, magicite.

You get a lot of gems from daily activities like collecting from the Infinity Tower and Ranked Match. The Camp Gem Mine is also helpful. Weekly rewards from PvP can add up, so try to place as high as you can in team PvP and duel PvP each week (3 matches to place) and stay on top of Ranked Match by challenging when you see higher-ranked opponents you have a good chance of winning against.

//todo: list of sources