A small town without any gym here, there is currently nothing much to be done here at the moment. However, Lavender Town is the first location where ‘Great Ball’ is sold in the Pokémart, therefore you can perhaps get your hand on some of these, as they have a slightly higher success rate than ‘Poké Ball’ in catching Pokémon.
There is the famous Lavender Tower in this little town, where Cubone and Ghost-type Pokémon resides in it. The top floor will be out of bound for the time being until you return with a Silph Scope. Before you leave the town, you should catch a Gastly on the third floor of Lavender Tower. Being a Ghost-type, Gastly and its evolution lines are immune to Normal and Fighting-type attack. Besides, its ability Levitate allows it to ignore Ground-type moves too. With its high speed and special attack, it will be of great help for Saffron Gym and many other battles.