Here's what you can do in that regard:
~First thing to keep in mind: The current format for tournaments is HeartGold/SoulSilver and newer. Any sets older than that cannot be used in tournament play (though casual play is fine). The exception would be if a card from an older set has since been reprinted in a legal one. For example, Switch is legal, and I'm pretty sure it always has been. Basic Energy are also always legal, and both have been reprinted countless times.
~You will probably want to find a starter deck at a store somewhere near you (like Target). The best choice would probably be one of the two Next Destinies starter decks - the figureheads are Reshiram (EXplosive Edge) and Zekrom (Voltage VortEX), respectively, and both of those cards are very big right now.
~The starter decks come with a rulebook, some damage counters, burn/poison markers, a coin, and iirc one booster pack. Familiarize yourself with the rulebook; it'll tell you what you need to know.
~Lastly, there's the matter of leagues. A league is a group of people that meet once a week to play the Pokemon TCG, and also hang out and have fun while you're at it. Since pretty much everyone there will play the TCG, you can trade for whatever cards you need; some people do still collect older cards! To find a league near you,
use this link.
I had better be the first reply or I may flip.