Usually legal review of the duty description and credential route, translation of any non-English documents, a credential evaluation if one is used, and the applicant's own time gathering employment confirmations. Government fees depend on the route and should be confirmed against current published amounts.
Spend first on the duty description
The duty description is where a documentation role most often runs into trouble, so reviewing the employer's draft letter is usually the most useful early expense. Evaluations and translations only help once the qualifying route is settled; commissioning them beforehand can mean paying for documents the case never needed. Ask whether the employer covers any of these costs before assuming either side will.
Order the spending: review of the employer letter first, then the decision on the credential route, then translation and any evaluation once that route is fixed. Reversing the order is what produces an evaluation of the wrong award. Ask the employer plainly whether their counsel drafts the support letter or expects the applicant to supply a draft, because the two arrangements put the cost and the control of the wording in different hands.
Hypothetical example: a contract packaging firm for pharmaceutical products tells a prospective writer that legal is handled, which turns out to mean corporate counsel reviews the letter without advising the individual on the profession or the credential route; that review remains the applicant's to arrange, and discovering it late is what delays the file.