Lowering a 2000 323i

I am looking to lower my 323i. I am not sure what exactly i need or dont need. I am curious to know if i have to buy a whole new suspension system or if i can just get new springs for it to go with the existing bmw suspension system. Will the existing suspension system support new springs? and will it be sufficient? Or will it mess up my entire suspension and ride of the car? In either case, which would be a good brand to buy?

- Please help me out, im new at this so all the suggestions and comments are welcomed. Thanks for your time and hope to hear from you all.