This is usually the most difficult question to address. It takes a little willingness to gamble on both sides. You don’t want to give a full months allowance and never see her again after meeting once, and she does not want to give you what you are looking for, receive nothing, and never see you again. If you have not already read it please see my post The Allowance Discussion https://wordpress.com/block-editor/post/howtobeasplendadaddy.com/186
Because this blog is NOT for the filthy rich Sugar Daddy that has endless amounts of money to spend on his Sugar Baby, but for a moderately well off man, the type of woman you will most likely attract and find may have little or no experience with this type of relationship. If this is the case, she needs to be assured that she can change her mind, and back out at anytime. This is especially important after the first time.
Remember the chances are very good that she will come to you at some point in the future, and want or need a full monthly allowance all at one time. My general rule is three months in this case. But in the end, it must be your decision, and how much risk you are willing to take.