Do not know what ifla is. Anyway, you need to first decide if you want physical or chemical conjugation. Then you have the issue of stability.

It is for chemical conjugation... the coupling is for Imunolateral Flow Assays...

The mAb is comparatively more difficult to conjugate, especially chemically conjugate than the polyclonals. The standing pH of the mAb will be better, otherwise choose pH based on the charge of the biomolecule, also relate to the isoelectric point. Consult a few articles. The amount can be equimolar (milli Moles) but how least material you can detect? Increase your molar ratios in decimal (1 to 1.1 mM, etc.) increments.

We do lateral flow assays with both chemical and physical coupling. Physical coupling is pretty simple. See Hermanson's book (Bioconjugate techniques) for details. In there you can also learn how to do chemical coupling. Unfortunately, details from the chemical coupling I cannot share.

Dear Guilherme Marcondes thank you for asking this very interesting technical question. I hope that the following potentialy useful articles will help you in your analysis:

Preparation of Colloidal Gold Particles and Conjugation to Protein A, IgG, F(ab’)2, and Streptavidin

Article Preparation of Colloidal Gold Particles and Conjugation to P...

and

Development of a Colloidal Gold Kit for the Diagnosis of Severe Fever with Thrombocytopenia Syndrome Virus Infection

Article Development of a Colloidal Gold Kit for the Diagnosis of Sev...

Both articles are freely available as public full texts on RG.

Good luck with your research!