SHOULD I SPEND THIS MONEY ON WEED?

ask him for less weed... if he's selling you 10 grams for 100$ that equals out to be 10 dollars a gram... (which is a great price for high quality weed)... See if he'll give you 3.5 grams (an eighth) for around 40 bucks. This will allow you to get high for a few days, and still have money left over.