My wife-to-be runs a pub, so I reckon she could sort me out with bottles.
I give it a year before one of you suggests a microbrewery!
Most upgrades fall into 3 categories:
*Stuff that makes brewing easier - star-san, bottle washers and drying tree's, corny keg and kegerator sytems etc.
*Stuff that makes better beer - going all grain, or extract brewing rather than kits, fermentation fridge.
*Stuff that makes it more 'pro'. Stainless or conical fermenters (or even stainless conicals), big gas fired all grain setups, plate exchangers your own yeast lab, etc.
There's something in homebrewing for everyone, which rabbit hole of endless upgrades you want to fall down is upto you:
Biologist - start a yeast lab
Electrical engineer - Fully PID controlled all grain setup
Accountant - tax code around setting up and selling beer from your 'microbrewery'
Quality Control - go become a beer judge / somelier
And the best bit, thanks to the internet we can now argue about it almost constantly, can you taste star-san, are plate exchangers really a workaround for commercial brewers rather than being the best solution and do immersion chillers produce brighter beer, how many times can you re-use the same yeast, is XXXX yeast really just re packaged Nottingham??