1/2 and 1/3 aren't that different for the most part in terms of quality of play. Some 1/3 games play small with most people in for $300 or less, some play more like 2/5.
If you can beat micro stakes online, you can beat live 1/3. There is no better way to learn what it's like that to just get in there. If they money doesn't hurt you at all, and you are comfortable playing deeper, I'd just buy in for the max.
Things to keep in mind. Live rake is usually in the 10% $7-$9 max range. You need to play pretty tight to beat this, especially if everyone is playing at $300 or less. Live raise sizes can be quite big. Expect opens from $10-$20. This effectively makes the game play even shorter than 100bb.
Some general live advice for your first time:
Focus on getting value from your good hands rather than bluffing. You will go multiway a lot, and bluffing requires more nuance multiway.
Don't be afraid to make big jams pre. If some opens to 15 and gets 3 callers before it gets to you and you have TT+, AQ+, you should really consider just jamming out you have 300. Once the pot represents 15-20% of your stack, jamming is never a terrible option if your hand is pretty strong.
No one really pays attention to your image. You could have not played a hand for an hour and then come in for a raise, and 3-4 people might still call.
Stay away from calling with suited connectors, especially out of position and multiway. Because opens are large and stacks are shallow, you often just aren't getting enough implied odds. And because so many live players play suited up and down (KXs AXa) it's easier to lose flush over flush than you might think. When shallower, high card strength and out kicking people has more value.
Most live players play very face up. This will be a bit more player dependent, but in general, live players at low stakes really do bet according to their hand strength. Smaller bets are often weaker and bigger bets are often stronger. Not to say there are also plenty of players than try to milk their big hands though. But when they just call on more connected boards, they often have at best top pair or a draw, and when they raise they have 2 pair plus. On dry boards though, they will slowplay more often.
Live players generally underbluff. Keep that in mind when you have strong hands, the obvious draw gets there, and they lead into you.
