Yes, I am blonde and unfortunately fit the myths. On the first page of BS, General, It has purchase settings.... Reserve amount and Maximum amount. Ok, in language that a 5 year old can understand...lol...what exactly is suppose to be put there? Is it how much I am willing to spend on just one item or several or do I even have the right idea?
reserve is the amount you want to be sure never to have less than on your toon. so if you put in a reserve of 500g, and you currently have 510g, and an item which normally sells for 1000g is listed for 20g...you are out of luck, because by buying the 20g item you will fall below your 500g reserve, so BTM won't suggest it for you. if you are comfortable managing your own money, just set this to 1 copper. It was mainly needed way back in the day when BF could automatically buy things.
maximum is just the highest price you will pay for any one (stack of) item(s) on the AH. If your max is 100g, and an item worth 2000g is listed for 110g, you will once again be out of luck.