Estimate by city and day of movement, don't rely solely on a national daily average. Expensive transfers and peak season dates often have a greater impact on total prices than meals.
Separate fixed and elastic costs
Transportation, core accommodations, and tickets are best protected first; Dining, short trips, and optional experiences require a practical buffer.
Spend money on places that can change your day
A better-located hotel, easier transfers, or a well-chosen guide at once are often more valuable than adding many paid attractions.