I did that. I used the money to give everyone a free shirt that came to the Highland league more than 5 times. I keep an eye open at all times when I am out shopping. I often look for frisbee related items that are suddenly on sale or marked down. Nerf footballs for example are relatively inexpensive and make great c.t.p. gifts.
Organization is key.
Keep track of all your expenses. Also, if I happened to be in the hole a particular week I would know to try and cut corners the next week. Disc sales are key to a positive money flow. Ask people that come to the league what they want to buy and try to get it. A good strategy for getting a lot of people to come to your league is to start league the week directly after another popular league ends.