I agree with checking the oil first, if thats ok, does the gears engage ok with the engine off? If yes the clutch might not be disengaging properly, the first motion shaft splines might not be clean allowing the boss to slide or the spigot bush is somehow snagging and continuing to turn the first motion shaft, and of course the clutch hydraulics after a few pumps of the pedal it might be disengaging the clutch better.
All this doesnt account for the noise!!
Keep us posted