It is a bit of a broad of a question to have a definitive answer since it depends on the complexity of your ligand, how reliable the bond lengths are currently (and how/if you're incorporating rotatable bonds during the Vina docking), and the end goal of the application. Not totally sure at what level you're considering doing the optimization, but also keep in mind Vina has its own quick optimization that is shown in their example, and takes nearly no time at all https://autodock-vina.readthedocs.io/en/latest/docking_python.html.

Thank you for this technical question. In the case of docking with AutoDock or Vina, they use bond length and angle during calculation of energy. Therefore a correct value of length and angle is required for correct energy values.

Optimization of ligand coordinates is very much essential. You can use MM of ChemDraw, Avogadro for optimization, if ligand size is very large. Definitely Gaussian is best for optimization but you can use above mentioned softwares.

Thanks. I drew the structures and did a 3D optimisation with Marwin. Then used avigadro to optimise the energy. Thank you all for your answers.