What's looking the best way to ready for raiding.
Probably some crafted gear (2 pieces)
World bosses.
Proving grounds daily gives lfr quality drop each day?
Then after that your looking at hc dungeons until lfr becomes available.
Anything else?
You are mistaken Challenge Mode dailies with Proving Grounds; it's the Challenge mode dailies that give epic loot.
Also there might be something similar to the Black Market which may or may not have current tier gear.
Then there is valor gear ofc which will probably be good untill you get into normal raids. There might be some decent rewards from epic questlines of getting exalted with a faction.
It will probably look something like this before going into raids.
Crafted gear
World boss
Black Market items (if you are rich)
HC dungeons / valor items
Exalted / quest rewards (getting exalted in 1 week might not be possible)
Challenge Mode dailies