Actually - $2.99 for a commercial clump like that is pretty darn good. A small plastic clamshell of little cut sprigs runs a minimum of $2.49 around here, & you have an excellent chance of keeping yours going for awhile.
Oh, & take it OUT OF THE SUN or it will be dead, if it isn't already!! Something like that needs to be slowly acclimated to full sun. You can't just plop it in a pot & stick it out in the sun right after it's been uprooted, shipped, & stored in an alien environment like a store. It should be in shade at first until it perks up, then just indirect bright light, & then increased sunlight for a few hours a day.
Even then - while basil is super easy to grow from seeds or small transplants, it can be temperamental when it comes to larger plants. Consider this an experiement, & if it doesn't perk up quickly, just use it in a sauce or something before it totally frizzles.