If you are trying to dress fancy, wearing the same outfit with a tie will be perceived as more fancy/professional, and slightly more casual without. I would say maybe get only one or two for weddings, funerals, etc. if you aren't in a job requiring you to dress professionally every day.
Also, don't buy new. Ties are one of those things were thrift shops always have an overabundance of. So you can usually find one or two that look good fairly cheaply there.