Is this for picking up sound off a pa, or shooting scenes?
If its a PA, taking a feed from the pa should be easy with a 40db pad if its a line level into a mic input on the camera. Minimum cost for a couple of adapters and a pad and cable.
If its shooting, as a minimum go for a boom pole, directional rifle mic and a cable back to the camera AND HEADPHONES. This will allow closer audio pickup all round. Theres plenty of choices on ebay so it doesnt need to cost much.
Going up theres a small mixer, batteries, cans, radio mics etc but thats a whole extra cost level.
How much do you have
Peter
Post Production Dubbing Mixer