Call your cousin
You may buy anything on the shelves with confidence, IF there were any brands of anything to 'avoid' they would have been removed from the market long ago.
Hold on there, Ranger.
Not everything on the shelves is good for rifle cartridges, much less a specific chambering (308 Winchester), nor for learning with.
For instance, I would not recommend Bullseye for the 308, even though it is a great powder for small cases at moderate power levels. Trail Boss is great for novices, as it occupies a lot of volume, but the maker recommends AGAINST using with jacketed bullets. Both great powders, but not for THAT intended purpose.
I don't have a personal recommendation for the OP, but disagree with the suggestion that any powder he finds on a shelf will fit his current need; something to learn with.
To jmichael99 (the OP), I just suggest picking up the phone and asking his cousin what powder. As Funshooter45 suggested, perhaps he has a powder in mind already that he has on his shelves. Besides, the powder you learn to load with is likely not going to be the one that becomes your favorite. Learning the mechanics of loading, operating the press without pinching your fingers does not depend on the powder used. You just want something forgiving and safe. After you learn the mechanics, then you can go to fine tuning, including selecting powders.
Besides, buying a whole pound of powder might be wasteful. There are plenty of handloaders who have three quarters of a pound of powder that showed promise which did not work out (for that particular gun, bullet, whatever). Your cousin may have 20 of those just wanting to be used up in a teaching situation.
Welcome to reloading, congratulations on your decision and on finding a mentor.
Lost Sheep