Well, I'm not a big expert grower but water treatment is my business so here's a couple of thoughts:
Regular inline carbon filters do not reduce your TDS count, in some cases it may even increase it. They do however reduce certain impurities, particularly chlorine and other VOC's (volatile organic chemicals).
A normal sediment filter also isn't going to do much for your TDS.
To reduce your TDS reverse osmosis is pretty much the way to go or you can use a so-called DI (De-Ionization) filter. The advantage of RO over DI is that RO removes pretty much every impurity that is in the water. DI does not, but it does bring your TDS way down and doesn't waste any water.
Regarding RO waste water, there are systems that simply recycle the waste water back into your water line which then ends up as shower, dish washing, hand washing water or whatever you use water for that doesn't come from your dedicated RO faucet. This is ok as long as you don't have excessive amounts of toxins in your water but personally I don't like it.
You should plumb the RO to a drain so you don't have to worry about the waste water or you can simply drain to a shower or sink in your house.

If you provide more specific information about your setup I'll be happy to give suggestions on how to set it up.

Peace!