Theres no way of answering this question without knowing what industry you are in and what products you are selling. Your costs are all dictated by how much you have to spend and how expensive the market you are operating in is.
It is all then determined by how much you are getting out of the spend in terms of profit. you shouldnt limit your budget if you are genrating a return as the more you spend at the right CPC level the more you make.
Use Google’s traffic estimator to see how much it says you could spend and decide on a budget that you can afford for the first month. Once you are confident of the return you will see remove the cap and reinvest the profit to grow the business.
Traditional rule of thumb is to allocate 10 to 15% of your goal or gross potential towards marketing / advertising. That’s all total. If you’re using Google Adwords only, 100% of your budget would go there. But if you’re using Adwords, Yahoo! Search and MicroSoft Ad Center, you could split the budget equally, or allocate according to program size: 1. Google, 2. Yahoo, 3. MSN.
Its depend on your budget, if you are new you should start with minimum budget. So that you can have an idea as how much are earning from there. If its profitable for you then start with big amount otherwise its better to loose little bit than a lot.
I hope this help you.
Good Luck!!