[New player questions! Help me please!]

I'm kinda a "new" player, i played Warframe when it came out with a another account but i didn't keep playing because i had no idea what to do, now i'm back and have some questions:

1- After defeating Vor what do i do? Do i keep clearing Earth map or go to Venus or Mars 1st?

2- I have now a mission (Saya's Vigil questline?) to do on Earth-Cetus-Plains which is a story i guess, i don't have a good pc so my frames goes to S#&$ there, can i skip somehow or i need to do those missions? If i need to do then, how many missions are there on the Plains? 

3- I wanna know about more about the Plains to try to avoid it, i seen that are some specific resources that you can get there, can i get it somewhere else? Are there more missions then Saya's Vigil there?

4- I keep looking at what Frame i should try to go to but i can't seen to find guides that help me, so maybe you guys(girls) can help by giving me some indications to what Frame i should go to, i normally like to play with characters(builds) that do area damage but i don't like to be like glass and die very easily, but the thing i like most and would play even if that it didn't have area damage would be like a push/rush character(build), im playing right now Excalibur, so which one you think i should got for?

5-Weapons!! Is there like a preferred weapon on the game like, "shotguns are OP", or is there like a "don't use that kinda of weapon because they suck", and any weapons i should avoid?

6- Does the episode is for everyone or only me? Because when i click on the episode status it shows me Nightwave - The Emissary, so is for everyone or just me?

Thanks for your help in advance!