A budget is useful when it helps you decide, not when it pretends to predict every rupee. Start with the total you can spend, then give each category a job.
Separate the big buckets
Estimate travel, accommodation, food, local transport and activities separately. If one number looks too high, you can adjust that category without rebuilding the entire trip.
Keep a real buffer
Set aside roughly ten percent for medicines, transport changes, weather surprises or the easier option you choose when everyone is tired. A buffer is part of the plan, not money you failed to allocate.
Spend on energy, not status
A direct transfer, a good location or a comfortable room can be worth more than adding one extra attraction. The best saving is usually the choice that prevents a stressful day.