The big categories are personnel (band and crew pay), per diems, travel (fuel, flights, vehicle or bus rental, tolls, parking), lodging, and production (backline, gear rental, lighting, and any production staff).
The ones people forget are what sink budgets: commissions to your booking agent and manager, insurance, work permits and visas, merch production and shipping, laundry, rehearsal days, and a contingency line for the surprises every tour brings. If you budget for those up front, the tour you planned is much closer to the tour you actually run.