Food & Drink
When keeping to a budget, eating out is best avoided, so make sure you have catered to suit everyone*. There are a few ways to do this. Firstly, you can get people to bring food with them and that way everyone contributes. Alternatively, you can wait until everyone is together, do a group shopping trip and spilt the final cost between everyone. Or, I recommend being a bit organised and doing a few runs to the local shops / checking online before the event and get a rough cost for how much you think you are going to spend on food. Then incorporate this into the money you are asking each person to pay. This way, you can do the shopping trip the night before, and they turn up and the food is already bought. In their head, they aren't having to pay out anything extra as it was included in the “price”. Here is a list of frugal food choices to help inspire you.
*check in advance for allergies and dietary requirements so you can cater accordingly.