Costumes in Skyforge are a way for you to customize the way your character looks. Aesthetics aren't binary in Skyforge, you can look any way that you want from a Cryomancer who looks like a Barbarian to sitting around in your underwear - costumes (your armor) has no impact on game performance, so you can look anyway you wish! 

Skyforge's costume system works with its monetization system, but that doesn't specifically mean you have to pay to enjoy it. You get the components used to purchase it from a variety of means, which aren't limited to just IRL cash. 

Let's go over how costumes work, then the means in which you can obtain them. 

Costumes & The Style Room 

The Style Room is a tab on your inventory screen that goes over which costumes you own and allows you to select not only your costume, but also the color it comes in (each color has to be unlocked individually). Players will start the game with  Classic, Rocker, Rogue, Light Power Suit, Special Agent, and Fancy Costumes. Founders can also have the Exoskeleton and Dress Uniform available. Beyond that you'll need to purchase additional costumes. 

Costumes are a take it or leave it deal. You get everything with the costume or nothing at all, but that doesn't mean your ability to look unique is limited. You get not only color options, but the ability to change your earrings, hat, face accessories, and your face tattoo. So don't worry about not being the most unique snowflake in the game - there are options for that. 

If you want to respec your style, go to the research lab and right before Flavius is an NPC who will respec your appearance for a cost (first one is free). Additionally, while not part of the Style Room, mounts can be customized on the mount page. 

Celestial Threads 

To purchase a new costume, you'll need to go to the marketplace where you'll find them both on the Costume Tab (Celestial Thread purchases only) and the rare items tab (for a variety of secondary currencies). First up, Celestial Threads can be purchased for either credits or gems, depending on market value (currently 50 gems or 8400 credits for 400 threads). At the current exchange rate, the gems is the better deal, but that is likely to change. 

Celestial Threads can also be obtained by playing the game as an award from some missions and as a filler award once you reach your weekly cap on sparks. So they're easily farmable, and costumes cost anywhere from a few thousand to 100k threads. It's important to note that these are easier to farm once you've reached your spark limit for the week, although you can easily convert either credits or gems into them if you want a look "now."

Other resources for various outfits are gained through gathering on maps. The resources are listed in their cost and these are available on the Rare Items tab.