To defeat the first gym leader with ease choose treeko as your starter pokemon then train it until it learns absorb and make sure it is strong enough to fight roxanne the first gym leader. send out treeko first and keep using absorb and her pokemon will faint quite easily because if you talk to the guy at the front of the inside of the gym he says that roxanne's pokemon is weak against grass types so that is why it is so easy to beat her with treeko.