I use NFT and to be honest, not really been worrying about PPM as I'm sticking to the feeding schedule pretty tightly, the nutes I use (Ionic) are very basic as well, certainly not the best and I'll be changing but they are really hard to over dose on, you gotta be going crazy.
As for my PH, I usually have 20 litres of water ready all the time, so it usually sits about 3 days in gallon bottles, I never have a problem with my PH being unstable. I believe my nutes the Ionics are good at that as well.
I have found NFT growing to be nothing but good experience, my auto's are massive compared to what I expected and my root growth is something else. Literally, my roots are now into the reservoir itself sucking up the water and feed. My NFT tray is nothing but roots.
Keep it simple, look after your PH, always have Bicarbonate soda (or a chemical PH up) and PH Down at hand and use nutes that are simple to use for your first grow and buy some mineral water in gallon containers, so you can fill those containers in advance with water, seems to help me keep my ph stable also.
I could recommend a timer for your NFT water pump as well, you can set it to feed twice a day for 15 mins a time until your roots are big enough to take it 24/7 (when they are popping out the large grodan cubes).
Thats about all the advice I can give you friend, good luck with your first grow and read up on NFT as much as you can, it's a great way to grow IMHO.
