It'd be cool if Lugia had a Flying quick move so he'd be one of the few mons with a double flying move...There are others with higher attack having dual flying moves, but most are 3 bar moves and I think Sky Attack is probably the best Flying move (2 bars, 2 sec cool down) so maybe he'd at least have a niche use...
Fearow seems to be the one with Sky Attack as well and Peck...
I would probably wait till raid bosses rotate before using TMs or powering up for now.
With your candies and dust, just do whatever you want and enjoy the game I think...
You have enough to max out other legendaries or other mons so no need to overthink it.