While there is not much that can be done here until you obtain the Bicycle, you can find a Machop here to help in the upcoming Gym match, especially if you started with Chimchar. You can also pick up a couple of Poké Balls in the grass.
Be aware that there are some Berries planted, but you cannot reach them until you get the second Badge. If you don't want the Berry plants to die, do not go too far north or try getting the items.
In order to battle the Gym Leader, Roark, you need to speak to him in the Oreburgh Mine. He can be found in the basement. After he shows you Rock Smash, he returns to the Gym and will wait there for you to challenge him. There are two Workers for you to battle here and a few items to pick up. You can also find wild Onix here, which can be a good addition to your team if you can later evolve it into Steelix through trade, but is otherwise probably not worth the effort.
Heal your Pokémon before entering the Gym. The Gym battle can be tough. It is recommended that you train your Pokémon until they're at Level 13 or more.
It's now time for your first Gym battle. The Oreburgh Gym is pretty straightforward and has no puzzles, though it is possible to take the raised path and avoid the two Trainers present. However, the Trainers are pretty easy to beat, and it's always good to gain some extra money and experience.
After the battle, the Grunts run off. Professor Rowan explains that they are part of Team Galactic, a villainous group that seeks power from Pokémon evolution for some nefarious purpose. Rowan explains that Pokémon release some type of energy when they evolve, but he believes it is a "mystic power" beyond human control. After he and Lucas/Dawn leave, a man from Jubilife TV gives you a Fashion Case, which can hold accessories and backdrops, and tells you that the TV station is now open to visitors.
Additionally, the Global Trade Station will also be open. You can also collect a new application program for your Pokétch.
The Fun-and-Games TV Station!
This building is where the dailylottery is held, where you can receive prizes if one of your Pokémon's Trainer ID numbers matches the random number drawn. You can participate the lottery at the counter in the ground floor lobby.
Additionally, there is always a Trainer in the ground floor lobby that you can battle once per day, but the Trainer that appears depends on the day of the week. On Thursday, there will be a pair of Interviewers (a Reporter and a Cameraman), and the battle will be your first Double Battle.
On the second floor, you can go inside the Ranking Rooms to access your game records.
There is nothing to do on the third floor, other than talking to some people.
Global Trade Station (GTS)
Outside of the GTS
Inside the GTS
The Global Trade Station (GTS for short) is the worldwide network over which you can trade Pokémon via the Nintendo Wi-Fi Connection. Now that you have Coal Badge, the GTS is also open. There is a large globe called the Geonet, which you can indicate their location, and on which small dots representing players you have traded with will appear. When you first logs on to Geonet, you will be asked where you live in. Talk to the woman at the counter. She will direct you into a room in which you can either put up a Pokémon to be traded or trade a Pokémon you own for one that has been put up.
Pokémon searches, after being confined to one species that has been seen by the player, can be further narrowed down to level, gender and the country where the person is trading it from is. By level, players can search for and request Pokémon Lv.9 or below, Lv.10 or above, Lv.20 or above and so on until Lv.100, or they can search for Pokémon of any level. Gender is similar, with the player being able to search for male, female or either gender of the selected Pokémon; searching for genderless species automatically sets the gender to 'either'.
Pokémon offerings are similarly governed, as the requested Pokémon in return cannot be any Pokémon that the player has not seen. Pokémon that are offered cannot be bargained, as the player has to choose one Pokémon he or she wants for it, instead of having a more flexible list. Like normal trades, a Pokémon can also hold an item when being offered or traded. Pokémon that evolve after a trade will do so in the same manner they would after a normal trade. The GTS also allows individuals to trade between two different games without having two Nintendo DS systems. It is recommended to check up on a deposited Pokémon every so often, as the Pokémon may flee if it is kept in the GTS for an extended period of time.
Go to the Pokétch Company and talk to the owner. He will give you a new application program (abbreviated as App, just like iPhone and Android Apps in your real life) Memo Pad for your Pokétch. Talk to him again and he will say that the next App will be ready when you have 3 Gym Badges.
Now heal your Pokémon and head north to Route 204.
You were able to access the southern part of Route 204 before going to Oreburgh City, but if you haven't already, pick up the Parlyz Heal and battle the trainers here. Now that you can use Rock Smash, you can get through the Ravaged Path, which connects the southern and northern parts of the route.
Make sure that you have Pokémon with Rock Smash before heading into the cave.
There's not much you can do here, except pick up the Antidote and use Rock Smash to find TM39 (Rock Tomb) to the west. Without Surf, you can't go any deeper, so go through the cave to the east and continue north.