The only thread I always follow is the Best Deals thread.
@Marq1340 posts some good deals there every few days or so. Other than that, I follow some threads from my state.
As a new hydroponic grower, I recommend you peruse the hydroponics threads and search for "DIY" or "D.I.Y." including the name of your preferred method. If you read through StinkBud's thread that I posted above, you'll find some good diy info.
The hardware and grow media you need will depend on the technique you choose.
I buy a lot of stuff off of Amazon. There are many options for nutrients. I use GH Flora series plus some supplements. I buy needed hardware at home depot, because it's the most convenient for me to access.
I have bought quite a few items off of growgreenmi.com. Check their Dank Deals link. They have some very good prices come up from time to time. The postings vary a lot, so I check it every few days to see if there's a gem in there.