Depends how pure of a possession WR your intent on crafting as to how you approach it. The eseentials early on for a PWR are the ability to pull passes in, and then you need to work on the ability to get open and raise the amount of times your targeted. Speed in reality for a PWR is a very low priority, as your role in the lower levels is simply to be a safe pair of hands when others aren't, so i'd work it late.
Personal preference would be, having built a PWR now to lvl51;
Catching to 60 cap-It's not a standout stat on it's own, but it is the keystone stat to a PWR build, without solid catching, all else is worthless
Agility to 67 cap-Agility has the advantage if being important both in getting open, and in terms of making catches, it's an all purpose stat that if raised early on helps a build in terms of reliability longterm. Again it won't make you a standout player, but it will get you in the game.
Vision to 60 cap-Now more important with the reaction rolls than before, it also enables small adjustments to routes by the WR and works well with agility in a PWR build. I only have it to 50 myself as I came to the stat late, but longterm it'll be worth getting to 60.
Speed to 60 cap-All you need for a PWR, 50 will do but 60 gets you to a sweetspot where you can operate longer routes as well as the short possession routes, it gives your build a lot of versatility.
Jumping to 67 cap-Only to be worked once you have the other stats in place, this benefits a build strongly when the supporting stats exist to compliment it. Before that it's pretty much useless. As a PWR i'd be training strength-jumping longterm from about lvl25-lvl40 to get them both up naturally, while raising other stats, you want them in, but high is not a necessity until later stages.
Strength to 50 cap-You want ideally 30 strength minimum on any PWR build, so get it training up at latest from lvl25, it contributes heavily to the catching rolls, and as a bonus is the point when the bruiser VA activates, which is real useful against a lot of CBs, is a good compliment to an otherwise completed build.
That should take you all the way past lvl50, as i'm only just reaching it now with my PWR that wasn't slow built, I reckon it should be a completeable target a little quicker if planned.