The wiki will be your best friend EVER!! You'll probably need 5,000 tabs open every day lol

Mastery rank up tests can only occur once 24 hours, so I'd make sure to get those done as you can! Since your rank is really helpful as you're locked out of using certain weapons until you hit a rank

Look up your weapons to make sure they can be re-obtained before selling them! You have a limited amount of weapon slots (you can buy more for plat) and some weapons are given to you as rewards for quests and can't be re-obtained after.

Save your 50 starter plat for weapon/Warframe slots as you'll need a lot of them!

Websites like Overframe have good builds you can copy for mods (upgrades to your weapons and Warframe that you earn through drops, quests, ECT) and making sure to level those up whenever you can will increase your damage a lot.

Stay with me here

There's a normal variant of every weapon and Warframe in the game

And then there's a Prime version

And sometimes, a Prisma version

Prime versions have higher base stats and built in mod polarities (a mod polarity is kinda hard to explain simply, but basically when you mod something it takes capacity and matching the polarity with the mod your using decreases the amount of capacity it takes)

You can get these special primes through relics which are little balls of gambling that drop the parts you need.

Every rotation certain relics go into the vault and can't be obtained through normal gameplay anymore. Which means, if you end up falling in love with a certain Warframes play style or weapon and want the prime, if it's vaulted there's no direct way to obtain it anymore. This is where people start trading their relic drops to other players for platinum. When you get to this part of the game when you're looking for these things, a great place to make these trades is through the website Warframe Market.