You say "rookie card" like there will only be one. He'll have about 45 different ones, from different brands released throughout the year, and from different companies. Some will be autographed, some will be jersey cards, some will be both, many will be serial numbered, some will be plain in the cheap brands.
And of course that's just the "normal" cards. There'll be hundreds of parallels, inserts, and memorabilia cards. As for brands, SP Authentic is usually seen as the most desired one, SPx a little behind hit.
That said, what are your motives here? If it's profit, there's likely none to be had here. These cards are going to be selling for hundreds of dollars right from the beginning, and their value will almost surely never be higher than it is at the beginning. The only profit in cards is usually by the sellers, who've been lucky enough to pull the cards in the first place. And of course, they usually had to spend thousands busting wax to find the card in the first place, so they usually don't profit either.
If it's collecting, then some advice is to decide what you want to collect and stick to only that. You won't be able to collect all of his cards like in the old days. Way too many low numbered inserts for that kind of thing. Even his base cards are going to be way too expensive for that.
So, I recommend waiting until an *attractive*, moderately priced card gets released, and then buy that one. I find a lot of the rookie cards are simply butt ugly, and their value simply comes from the rarity, not the beauty. I'd rather have a more common nice looking card than a rare ugly thing, but that's just me.