The budget is usually presented in a tabular form, listing the resource requirements for a successful execution of the project. Any position in this budget must be justified (linked to an objective, work package or activity) and explained (cost structure). The maximum amount of found is given by the donor.
Do not fit the budgetary requirements of your research project to the donor limits. Plan your resource requirements realistically. If the donor limit does not allow you to reasonably and realistically conduct your planned research, you either slim down your research plan and drop work packages or activities (possible elements for a future follow-up proposal) or you do not submit your proposal to this specific donor. If you accept a under-funded project and you fail to deliver the results because of this, it will be exclusively your fault, and you may never be eligible to submit a project to this donor again.
The categories for which funding may be requested usually comprise at least the four positions of Personnel, Equipment, Supplies, and Travel. Your budget must be transparent (why you request how much money for which position), requiring that each and every position is justified (indicate why this item is required for a given activity and in what way is will contribute to a milestone, a deliverable or the overall goal of your research) and explained (cost composition and structure with supporting offers, proforma or official quotes for the requested funding items).