Adrien Broner -- Check Out My 50 Karat Chain!! Drops $750k at Jeweler

Adrien Broner only knows one way to celebrate a dominating win -- well 750 ways ... cause TMZ Sports has learned he just scooped up a ton of fresh bling.

"The Problem," still feeling euphoric over his butt whipping of John Molina last month ... hit up Avianne and Co. in NYC and treated himself to $750k worth of ridiculous jewelry.

Avianne and Co. has hooked up the likes of Justin Bieber and Chris Brown, but AB's haul of custom pieces has to rival anything they bought.

Owner Joe Avianne tells us he copped 10 icy pieces -- some of the highlights:

- 50 karat diamond chain
- 10 karat diamond and platinum ring
- 30 karat custom Avianne watch with AB's initials
- 10 karat diamond earrings

Understatement of the century alert -- Avianne says Broner is one of his best customers.