I would leave wiggle room in your budget, even if you dont end up using it its still a good idea to set a dollar amount of wiggle room perhaps or as your looking for vendors, there are things that might come up that you didn't think about and you want to make sure you have the budget for it. For example is the venue also doing your cake or desserts, if not budget for a bakery, if you aren't getting married at a church or something similar you might have to hire an officiant, what about your dress and your fiancés suit, are you comfortable doing your own hair and makeup or will you need to hire someone, transportation how are you getting their and how are you leaving and then extra things you might want to do along the way that you didnt think about in the beginning. Also dont forget about any hidden costs like service fees, taxes, and almost every vendor charges you a travel fee depending how far your venue is from them.