I recently bought a new bike with full shimano deore 12 speed and was wondering what the best parts to upgrade first would be in terms of weight and performance. Currently thinking an XT shifter but not sure if there is anything else that will make a big difference. Thanks
Definately go the XT shifter. Much nicer than the Deore and you get the multi shift function in both directions. And a XT or XTR chain. I find they corode MUCH less than Deore. I'd also consider an SLX crankset. Zero performance benefit but it's significantly lighter than the Deore. The XT is only a few grams lighter than teh SLX. And once the cassette wears out, get an SLX or XT. Also a fair bit lighter.
Or, just keep it all. Deore is pretty damn good now.