Yes. Leveling renown unlocks conduit slots and soul bind passives.
You should unlock all the conduits you are going to use. The difference in ilvl does also make a significant impact.
You can, but it’s not the most efficient. Supplementing raid gear with M+ drops is your best bet. If you are truely just starting out, Korthia gear will be a good start.
Well I believe that you need an ilevel of 195 for Sanctum of Domination LFR. So you will have to work towards that goal via timewalking, dungeons and your convenient renown. If your guild runs raids they might allow you to tag along for normal before you reach that level. Either way you will have to grind out some better gear. As the poster above me said Korthia gear is your best bet for gearing but don’t forget renown and conduits.
When I first started raiding normal/heroic I watched a quick rundown of the boss fight that is around 3-5 minutes long, ran a bit of mythic +10s to get my ilvl up and asked the raid leader questions if I didn’t understand anything. I’ve seen people do the raids doing none of these things but often times they don’t do that well on the fights.
Yes I would recommend unlocking conduits and soul binds. For gear you can stick to only raids but your ilvl won’t improve by a lot and many desirable items are found in m+ dungeons that will help you in raid.
I farmed normal/heroic dungeons until I was in all blues and then I did LFR. Right now you can just buy iLvl 200 stuff from the AH (depends on the cost) and/or farm Korthia to get upgrades. You can also iLvl upgrade your Korthia gear as well.
To really gear up though I grinded a lot of M+. Start at low keys and work your way up as you get more experienced. You’ll get your conduits and legendary form that as well as Renown.
Might take you a few weeks, but you should be able to catch up to people.
You may also want some method of breaking through the noise and finding signal. Some mechanics have no impact on damage players and some are entirely damage mechanics. Addons like big Wigs and weakauras can help just give you eyes around the room.
Such as when adds appear. Mechanics you fail consistently can be hilighted to improve. Learning the graphics of soak/avoid/spread/stack mechanics is also pretty handy.