You can certainly use a kit - lots are available. However, it is possible to prep them if you have a decent strain that makes sufficient numbers for a miniprep. If you don't require high quality (intact, supercoiled) plasmid, then any standard lytic prep will work.  I haven't doe this for a few years, but I don't recall any issues with using a standard plasmid isolation preparation. This gave me sufficient masses for characterisation. However, I would recommend using a kit if you want very high quality DNA.