Rangers, Adidas 92/93 for me. I've always preferred Adidas to any other kit manufacturer, so I'm biased, but us getting an Adidas kit for me signalled an upgrade, we were the only Scottish club made by Adidas at that time and in that era it felt like they were mainly associating themselves with top clubs. It was a stunning kit too, and the return of the red and black socks which as a 10 year old I was learning for the first time was a big part of our tradition.
The upgrade was then reflected on the field with our treble the next season and us going toe to toe with Europe's best on our legendary Champions' League run. Super Ally winning the Golden Boot, Hateley not far off him, and Goram arguably the best keeper in the world that season. I feel like that was the season that kicked the 9iar era into a new phase, leading to Laudrup, Gazza and the wonderful times that followed. Not saying it was the kit that did it, but I always think that a great kit can make a difference around the margins of a squad's identity and performance.