When Heavensward was added, SE put in a lot of easy shortcuts for people to quickly get good level 50 gear that had previously taken a lot of grinding when 50 was endgame. I expect they'll they'll do the same with level 60 gear when Stormblood is added. If so, there's little need to gear up in advance, since you'll be able to more easily gear up when it hits. In the meantime, just collect whatever gear you want for the Heavensward content you'll be running between now and then.

PotD is one of the good ways to level. Personally, I prefer dungeons. FATEs and leves work too, along with any sidequests you have left over. One of the downsides by leveling by POTD is that your level within it is different than your level outside it, which makes learning the jobs harder. Doing your leveling roulette followed by whichever dungeon is closest to your level may be better at giving you experience (lowercase "e", as in actual practice with the job) as well as XP. And alternating among all the various ways of leveling is best for avoiding burnout from grinding the same thing the whole time. So look to the challenge log and your class hunting logs, leves, FATEs, dungeons, quests, POTD. There's lots of ways to gain XP, and most of the way through it goes pretty fast (only slowing down near the end).

I have multiple alts, and originally was planning to do everything with each of them, but the time commitment for even one character sort of overwhelmed me, and I ended up settling on Y'kayah as my main character. It's nice at the beginning, getting to see the different cities' storylines (the main scenario is different by city for the first 15 levels), as well as trying out different appearances. But it would take someone a bit more hardcore about it than me to actually level multiple characters to endgame. There are people who do that, though, and it has advantages for getting around caps and lockouts, letting you gear up multiple jobs by using a different character for each.

And yes, there should really be more Duskwights in the game. (One of my alts is one.)