New(ish) player to Warframe. A few questions to the Warframe veterans if you don't mind regarding inventory management

Like many new players here, being a hardcore Destiny player, I immediately fell in love with Warframe. The community is literally one of the best I've ever experienced in gaming.

I've used a lot of the helpful Reddit posts/YouTube guides to help me get to MR 15 with very little problem. I've mainly been ranking and using my few favourite weapons and I've made enough plat off trading to get nearly all of the Warframes. Now they are all levelled, I've hit the spot where I need to start ranking up the 100s of weapons that are available. So I was wondering:

1. How do you go about weapon management. Do you rank every single one up and keep it with a plan to mod/forma the weapons eventually. Or do you delete the weapon once you levelled it and only keep it if you like it?

2. The same sort of question goes to the mods. Do you just save duplicates of the rare mods for trading/helping new players?

Sorry if these seen like silly questions, just feeling overwhelmed at the moment with the amount of weapons and the amount of slots I might potentially need for them all.