A few pieces of information would help:
- What IS your budget? This can help determine what is and isn't available to you. If you've got money to burn, you can afford more durable, better looking materials. If you're going dirt cheap, you might need to use cheap/free materials to get by.
- What's your experience? What have you worked with? Are you wanting to learn a new material or technique, or do you want to perfect an existing method or stay in a comfort zone? We can point you in the right direction for relevant info if we know what you plan on working in.
- Time frame. How long do you have to make the prop? Do you have months to spend on it, or do you need it this weekend? The amount of available time can limit you to quicker materials, or allow you the time to learn and develop other methods.