Welcome BubbleBetta12 :)
Many of the stickies on these forums would actually answer your questions in extremely great detail.
In regards to plant choice, PewPewPew has written an excellent guide on aquatic plants here: (http://www.bettafish.com/showthread.php?t=76428
). As to why this is not a sticky yet, who knows! Aquatic plants look realistic (for obvious reasons), can assist a cycle and ammonia levels, and also improve tank qualities. On the other hand, they can also cause a bit more of a headache as a beginner – from personal experience. I currently have 2 anubias that are either going to live or die because I was unaware of the need to isolate an unwell Betta from a main tank when dosing medication. For this reason, if you do end up getting live plants, I recommend having a QT on standby for Betta if anything happens (Quarantine Tank), and also a good liquid fertiliser on hand to give them a fighting chance. Appropriate lighting will also be required as well depending on choice of plants.
Fake plants require almost no maintenance, and the only thing you must be careful with is the sharpness or snag possibilities of Betta’s fins. Running a pair of pantyhose across them, is a good test to see if they are suitable. Silk plants are preferable as they are softer.
Ultimately the choice is yours. Personally, I am prepared to switch to fake plants if my current living ones do not survive.
In regards to choosing a Petsmart Betta, it is recommend that a beginner chooses a healthy as possible. This way you have the greatest chance of success with him/her, without having to combat additional diseases that can be daunting to someone who is just starting. So if you chose to purchase your Betta from Petsmart, it is advisable to select the healthiest disease free one there, or, shop elsewhere, or, wait for a new shipment which most likely would be in relatively good condition.
Once you gain experience and knowledge like many on here (not myself), it is a breeze to take a sick fishy home, and see them mend and live healthy lives.