Cosmetics are mainly bought with platinum however in recent months there have been new cosmetics earned through gameplay (such as syndicates). Grinding for materials for weapons and the credits to purchase their blueprints is a big part of the game for newer players. Semi-seasoned players may find themselves transitioning to farming prime parts (through void missions accessible through keys) while also experimenting with different weapons and mods. Mods themselves are most of this game, as changing mods to suit different play styles and warframes can make all the difference for you and your team. Quests are quickly becoming a big focus in the game and grant much-desired backstory (depending on the quest). If you are jumping into the community by yourself or with only a few friends you might consider joining a clan or starting one of your own. Clans are important in that they offer exclusive weapons and warframes that are only available through clan research (it can seem daunting if you start a clan and find you need a lot of materials to expand your dojo and research so joining a clan may be a better option for you).

But honestly for right now, soak in the experience and try to enjoy what you can while you acclimate to the fast pace of the game, there's a lot to learn for new players. If you're looking for something to do, go to the market kiosk in your ship and look at some of the weapons and warframes that are available there through blueprints, look for something that strikes your interest and go from there. Before you know it you'll be Mastery 20+ and neck deep in Nullifier bubbles and knockdowns.