Assuming you've got 15 to spend for the playoffs
Boost once, then add to agility, then boost the other times. Otherwise naturals will take you over the cap, and you wont get to spend that 1 on agility! Neat little trick.
Then I'd 3:cap blocking which will take what, 9 points after natural gains, leaving 5 to put on vision. Cap it on your next level up.
I'd then continue to train agility + speed, most likely, as that 48 agility is your best value right now, and as a RG I personally favor spd/agi over vis/conf/sta.
For the future, you're probably looking to cap vision, cap speed, then look toward taking agility to 60 next season if you so desire, after you've had enough time to train it from 48 to 51 through most of the season, of course
Just my thoughts!