Start with a 30 size machine. The reason is that parts are cheaper to replace than larger machines. You will need aleast a 6 channel radio with 5 servos and a gyro to get in the air. A very good first heli is Thunder Tiger's Raptor 30. A stable trainer and parts are readily available and cheap. Again ,we would recommend an OS .32 engine for this set up. Keeping it simple and reliable is the key. Futaba's GY 401 gyro is the best choice.