Best to use 2 gRNAs since having an additional cut site increases the probability of a deletion that will cause a loss of function. Ideally you would transfect with Cas9 mRNA along with the gRNAs. You can transfect with multiple plasmids simultaneously but you get reduced yields of transformants. As for what plasmid is ideal you would need to check the promoters and if they work in your organism/cell type. ideally have cut sites about 100bp apart.

CRISPR-Cas9-mediated gene deletion is a powerful tool for genome editing, allowing precise removal of specific genomic regions. The best approach for CRISPR-Cas9-mediated gene deletion may vary depending on the specific experimental requirements, cell type, and desired outcome. However, careful design of gRNAs, efficient delivery of CRISPR components, thorough screening and validation, and rigorous off-target analysis are key considerations for successful gene deletion experiments. Additionally, optimization and iterative refinement of experimental procedures can help improve the efficiency and reliability of CRISPR-Cas9 editing.

I also suggest dual guide RNAs. Just try to avoid target sites that are an in-frame distance apart from each other, otherwise you might get a nice in-frame deletion and less functional disruption than if you get a frame-shifting sort of deletion.