I highly recommend that you get, at the very least, an automatic, self-levelling laser. If you have to set the level yourself, your accuracy will be much lower, and the setup will always be a PITA.
They have models that use a prism, or others that have a rotary mechanism. If you are planning on working with it outdoors at any point, you want to get a rotary laser.
I have a Robotoolz (now Porter Cable) rotary laser and absolutely love it! Cost a mint, but totally paid for itself. I would also recommend Stabila, TopCon, CST/Berger and White Rogers. You get what you pay for.