Professor Juniper and Bianca talk for a little while before Bianca heads east. Lentimas Town is very small, so there isn't much to do here. The Pokemon Center is in the middle of the town. An old woman inside gives a Spell Tag, which boosts the power of Ghost-type moves by 20% when held.
The house west of the Pokemon Center has a Move Tutor that accepts Blue Shards as payment. The house to the south has a Battle Girl that gives away TM 57 Charge Beam. It's an attack that deals damage and has a 70% chance of raising the user's Special Attack. The hill north of the Pokemon Center, which can be accessed at the north end of the runway, has a Fire Stone. Head east to the outside of Reversal Mountain when you're ready.