I have built up a collection of tools over the years some have become obsolete and new ones have appeared.
I was quite fortunate as all my bikes have an 'English' 68-73mm threaded bottom bracket.
I first started on a Cube LTD Race, 26er from around 2007. This had a Shimano triple. I bought all necessary upgrade kit from Evans Cycles.
When finished the bike was about 500g lighter ! I added some Absolute Black chainrings to my collection at this stage also.
Now the kits came with an 11-42 cassette, but I wanted more range so I purchased the One Up Shark which gave me 11-50 !! I also could increase the chainring to 34t or even 36t.
Above pic is not the finished article, this was a start there were more developments later on so stay tuned.