Anything and everything
It’s not often I buy stuff for vanity. So everythign from stiffer stem’s to grippier tyres is either to make riding better in some way and therefore longer or faster rides.
Brakes – I had no confidence in my old ones
Stem – old one wasn’t stiff enough, had a cheep temporary one that weighed ~300g so spashed out on a lighter one but it was still an upgrade from the original.
Dropper post – see the forum ad nauseum
Tyres – self explanatory
FS bike – self explanatory
new wheels – well the old ones weren’t round
forks – stiffer and better damped = more grip + more confidence = faster
It’s a hobby, I don’t begrudge people who spend more money than me on it. Similarly I can’t look down on people riding cheeper bikes as a) I’ve been there and didn’t enjoy cycing any less than I do now (it was just more fustrating and sometimes harder work) b) I’ve a rigid SS so know that it’s not about the kit!
Next upgrades – some coaching to iron out bad habits and I can’t decide whther I want stiffer wheels on the road bike. either will cost significantly more than my first MTB!