Most trainers, or probably the older community of trainers started their first Pokemon journey in the Kanto region. Charmander, Squirtle, and Bulbasaur are the starters you can get there. The Pokemon professor Samuel Oak is the one who gives trainers their starters, he studies Pokemon and human relations. The main goal when a trainer starts their journey is to challenge the Pokemon League. In order to challenge the Pokemon League you must gather the eight gym badges of the region.
The eight gym leaders of the Kanto region are Brock, Misty, Lt. Surge, Erika, Koga, Sabrina, Blaine, and Giovanni. However in the more modern versions of Kanto, Koga is in the Elite Four so his kid Janine takes over the gym. And the last gym leader of the Kanto region, Giovanni, quit for unknown reasons so Blue took over. The first thing you should do is to make sure you have enough Pokeballs and Potions, usually about three Potions and five Pokeballs work out good enough for the beginning of your journey.
You will go through Viridian Forest and find yourself in Pewter City. Pewter City is the place where the first gym leader is at. The gym leader is Brock, he trains rock type Pokemon. So it might be a little hard to beat him if you chose a Charmander as your starter Pokemon. This is because a rock type Pokemon has a type advantage over fire type Pokemon. Brock will use two Pokemon against you. These two pokemon are both duo types. This means instead of having one type they have two. In this case they a ground type and rock type Pokemon. The first he will use is a Geodude. The Geodude can be defeated quickly if you chose a Squirtle that probably learned Water Gun by now. Or a Bulbasaur that probably learned Absorb.
If you have enough potions and a few other Pokemon aside from your starter with you at this time it should make it a bit easier if you choose a Charmander. Don’t get me wrong, Charmander is a great and powerful starter, it’s just the first few gyms have a type advantage. If you win Brock will give you the Boulder Badge, the very first badge in the Kanto region. Only seven more to go! Next up is the water type gym in Cerulean City!