[bluepanda_]

Thanks for all the suggestions. To be more specific, my situation is that I'll be making $x this summer, in addition to making $y/month and spending $z/month. I need to visualize these data to determine whether I can afford to make that $x/k expense (i.e: expense that represents a part of x that is less than x) and still have a margin m, where m is defined as financial "safety". Sorry if it's confusing, but I hope it makes sense.

As smartician suggested, Mint is great to get an overview of one's finance, but it doesn't let me visualize the above amounts.

As ragatskynet suggested, spreadsheets are the most obvious choice, and the fact that I can "complicate them to the level [I] want" should allow me to plot the above amounts as I need, but I was trying to find a more elegant way to do this than using excel.

I will be looking into the other suggestions. stevekemp's seems to be just what I need.