light meter mostly use to take incident meter reading, it is more accurate than using the reflective meter reading with the camera meter, of course, the photographers must understand how the metering works and also how and where to take the meter reading from, else using the most accurate light meter will still get wrong readings.
light meter also very useful to take flash meter reading, which camera meter don't have such function.
I'm using a very old and basic Sekonic L-328, it serve me very well.
you can check out the mass sale section and the Virtual Shops, some of our advertisers are selling Sekonic meters.
I am using the L-358 and it is very good. I have used the 308s, the thing about 308s is you cannot do Aperture priority mode... But that is a minor issue, as nowadays most people use light meter for strobing. And most people fix shutter speed anyway for strobing work. Overall the 308s is a good basic and reliable flash light meter.