That's gonna be hard...frogs and supplies get expensive. 50 pounds is roughly 80 USD, and Including frogs, I just spent 120 USD on my recent tank, and that was low budget. If this is your first frog, I suggest 2 or 3 White's tree frogs. they are hardy, tolerant to handling, and easy to care for. You can take a look at my thread (Hexagon Vivarium journal/advice) for ideas. That tank is for 2 white's tree frogs. In the US, these frogs for for about 20 USD, so if they go for the same price there than they are around 12.5 pounds.