Reece is my go-to, then GSG. It's hard to beat "free" weekly truck deliveries.
If you order enough volume consistently from a single supplier they'll start lowering prices across the board. Just start a conversation with all the reps in your area and see which distributor is the best fit for you.
As
MarkSnelling pointed out, there's a TON of value in choosing a supplier that
really knows about the products they sell. Take their recommendations, use them, and share pics / give feedback of jobs you've completed. Build a relationship. You'll make more money with a good rep in your corner than you will trying to shave pennies off everything you buy.
I can't overstate this enough -- be super nice and respectful to your sales reps! Even when problems happen!
(they deal with nasty customers just like the rest of us). You'll get more leeway when negotiating, and might benefit from intangibles that aren't reflected on your invoice.
For example, there have been multiple times over the years where maybe I got shorted on something, received the wrong or damaged material or even me screwing up an important rush job, and my my sales rep drove 2 hours on a weekend to save my bacon. He's not gonna do that if he knows you'll drop him to save a nickel. Keep your rep happy and be loyal. It's worth it.
We're all paying higher prices -- just pass those costs onto your customers.