My main focus right now is definitely mods and weapons though! I'm enjoying my character now!

That is the right mindset! Mods are one of the most important aspects of the game.

I wanna get a Cernos, Paris/ParisPrime, and Dread. I already bought Cernos and Paris blueprints but the map simply doesn't give me the items I need. Should I just "pointlessly" grind through the planets to get new ones which will hopefully carry what I need?

Which is why it is important to unlock the other planets. Try joining a clan, and ask some of your clan mates to take you on farming runs on some of the planets that drop the bow resources.

Also, in terms of quest progression; What exactly am I looking at in the future? If the Kubrow and Archwing quests are more lategame, am I literally to just find my own goals now (the game is "over") or is there something I should be looking into?

Here is my difficulty interpretation of the current quests we have:

1) Vor's Prize: aka the tutorial quest, all new players should complete this

2) Once Awake: introduces new players to the Infested faction. spoilers you get a free melee weapon blueprint + a nice mod to go with it once you complete parts of the quest. (Beginner Player level)

3) Stolen Dreams (Requires mastery level 3): This mission is more for players who are getting the hang of this game. Loki makes this mission piss easy.

4) The Archwing (requires mastery rank 2): In my opinion new players should focus on the normal non archwing missions since archwing has a compeltely different set of mods. I rather prefer new players to devote their credits and resources to their warframe and weapon mods before tackling archwing.

For Advanced Players

5) Howl of Kubrow: Although straight forward to complete, the egg drop rate is rather low. An kubrows not that useful for new players really. The doggies require upkeep in the form of injectors that needs to be purchased in the market. For new players the cost of these "HP" potions to alleviate the kubrow's constantly deteriorating health is VERY high.

6) The Limbo Theorem: Requires archwings and is hard enough that you need to have a pretty well leveled archwing load out to even consider completeing this mission.

7) The Hidden Message: Mirage's quest is a more straight forward than limbo's, but you go against some high level infested. Definately not new player quest. You also need 5 orokin ciphers which are gained from orokin vaults found on orokin derelict missions. If that previous sentence sounded like gibberish, then you should not tackle this mission.

8) Patient Zero: the start to getting Mesa. Definately not for new players due to again high level infested.