You probably just beat the second gym leader in Azalea Town, am I correct? The next gym is in Goldenrod City. It should be fairly easy to get there from Azlea Town, just get past the Ilex Forest. Upon arriving in the town you will notice that this is a big city. I believe it is the biggest town in the Johto region. There is a lot to do here aside from the usual enter town and go to gym pattern. The radio tower is in this town. Visit and you could get a radio programmed into your PokeGear, you get it by answering some trivia questions.
After that you should check out the Game Corner. The Game Corner varies, there might be the usual with slots and what not or it could be a game with volt orbs and choosing the correct ones, if you click on a panel with a volt orb on it it will explode and you lose the coins you have won on that round. It is a pretty fun game. Now those are just some of the things to do here. There is also the Magnet Train that will later let you ride to Saffron City in Kanto. With that being said there is still much more to do in Goldenrod City, however, the gym is still important if you want to get your third badge. So why not check it out?
This gym happens to be a normal type gym, there is no weakness for normal type Pokemon except fighting types. If you have a fighting type Pokemon it will be a bit easier, but not by much. Not nearly by much. This gym happens to be one of the hardest, everyone probably had to try to be the leader more than once. Anyway let’s get on with the gym battle. The leader is Whitney, she is tough, don’t let her looks get in the way! The first Pokemon she will use is a Clefairy, this Clefairy has some power, don’t underestimate the power it has though, it will be pretty hard to take it down, but it will seem incredibly easy compared to her last Pokemon.
Whitney’s strongest Pokemon is a Miltank. This Miltank is hard to take down. It will use Attract on you, hopefully your Pokemon is the same gender. It will use a powerful Rollout attack that can quickly defeat you. And when you get its HP down it will use Milk Drink and restore its health. This Miltank is extremely hard, I know I said it like three times already but it is true, very true. If you can manage to defeat Whitney she will give you the Plain Badge. You will then have three badges, one five more to go before you can challenge the Pokemon League in Johto.