At 3rd level youve learned to create fragment grenades. These grenades cost 20 gp worth of materials and deal 3d4 damage in a 10 ft radius. You may create a maximum number of grenades equal to your Proficentcy bonus on any given day (Max 3 at a time). You can throw these grenades up to 30 ft.
At 7th level you may create an attatchment for a shotgun or rifle that shoots grenades a a distance equal to the stadard range of the weapon. This takes 25 gp worth of materials and takes 1 hour of work. In addition your grenades deal 4d4 damage.
At 11th level you have learned to imbue your grenades with Acid, Cold, Fire, Electric, Thunder, Nerotic or radiant damage. When a grenade is created you may choose a damage type and change the damge the grenade deals to this damage by using 10 gp worth of crystals during creation. In addition your grenades deal 5d4 damage.
At 15th level you have learned to engineer explosives with master quality. Your grenades deal 6d4 damage and you can create up to 2 * Proficentcy mod grenades in a day. As a bonus action, if you began the round with no grenades, you may use your action to create one.