My basic carry items are a decent folder, a flashlight, a BIC lighter, a ferro rod, some matches, a pair of nitril gloves, a few band aids and a first aid packet. The items except the folder and the flashlight are less than 20€ in total.
Anything on top of that will depend on the situation. The kit will consist of items I already have. So budget would not really be a concern.I aquired those items over time when I felt that I would need them ( or wanted a new toy ).