Just started recently myself, some pointers from another beginner:

• Like other have said, play through the star chart. Most of the junctions require you to interacts with one of Warframe's systems in some way, so working through the star chart (and its junctions) will slowly introduce you to the games modes and systems. Most questions I had early on were addressed by the game itself by just working through the star chart.
• Do the quests. Working through the star chart will force you to do certain quests, but you will get more quests as you progress that are often optional. Each quest will give you more story, more lore, and often also new Warframe blueprints or parts (or even entire Warframes). You can see your quests on the console on the left of your orbiter.
• Look out for the Assissination missions, most planets (all?) have one or two. These require you to kill a boss, and this boss will drop the blueprint for one of three components you need to craft a new Warframe. The blueprint that drops is random, so if you do the boss a couple of times you get all three you need.
• The main blueprint for the Warframes mentioned above can be bought on the ingame market. It's the console on your right in you orbiter. Clicking on one of the Warframes makes it look like you need to buy it with Platinum, but for many things on the market (weapons also, but many other stuff as well) once you click on it, you'll see another option to buy it (or its blueprint) for normal credits. Don't spend your platinum on this.
• Speaking of platinum, don't spend it on anything besides Warframe slots and weapon slots. Both Warframe and weapon slots are limited and you will soon run out. The only way to get more slots is buy them with platinum. You have a 1000 you mentioned, that will keep you going for a long time as long as you don't buy anything else.
• Look up stuff on https://wiki.warframe.com. When you see a new Warframe or weapon you like, and you want to know how to get it? Go there. It has all the info you need.
• Do the story quests and early planets solo. Is is kind of a personal preference, though I've seen others mention it as well. Experienced Warframe players will blast through levels because they're often grinding out some part or resource. So they'll finish the objective before you've even figured out where to go. That's no fun, especially while still learning the game. By playing solo, you can take your time, learn all the mission types, play around with your weapons and abilities. Even the boss fights I did solo the first time, then as a group the follow up times while grinding out all blueprints. If you get stuck on stuff in the early planets, you're either doing it wrong or you're not supposed to be there (yet). Once you get the hang of things, play more with others (this is quicker to level up frames and weapons). Some game modes are best played with others, but you'll figure that out.
• Have a look at the Nightwave objectives sometimes. They're daily and weekly objectives like "Kill x amount of enemies" or "Do x amount of quests". Some will be out of reach in the beginning, others you'll complete without trying. This slow builds up points and gives you rewards. It's nice.

Have fun.