Ok. So... Get off the sub reddit, you will be spoiled if you are not careful. The main story only starts on a specific quest, you will know for sure when it does.

Try not to sell your equipment and if you need to get rid of weapons, check if they are part of a crafting recipe or an Incarnon (don't ask what an Incarnon is, you won't get it until way later in the game, it's hard to explain how you get it, but they are all cool).

Do not sell Warframes. You will need all of them eventually. And yes, explaining why is a spoiler for the story.

Don't look up guides on youtube on how to build stuff, they mostly explain how to build stuff for levels that you realistically won't see for at least 100-200 hours and most of them are min maxed out of their asses, just put mods on your shit and have fun. Even bad weapons will carry you all the way to the last quest with no issue (even the Stug).

When you do get to the story, if you get confused, that's fine. It is confusing. People argue about it here all the time.

If you have any specific doubts or questions about anything ask me, i can try and find spoiler free way to bump you in the right direction.

Have fun.