Is your MTB a hardail or a rigid. If its rigid I really like the PB cascadias for fenders. If its a hardtail the PB Speedez work pretty well.

There is a lot of choice for rear lights. The PB Superflash turbo or Radbot 1000 should be good choices.

Tires usually recommended are the Panaracer T Servs, Schwalbe marathons, and Specialized Armadillos. I prefer good puncture resistant tires above all else.

Also don't forget about a lock and a multitool kit.

Good Luck.