Bike shops are asking 100+£ for a bike assemble and it might be justified but its too much for my budget and I want to DIY it.
Is that risky to do by watching youtube videos and borrowing tools from friends?
I want to install an english threaded bottom branket with a squared tappered crankset, disc brakes (mechanical), headset (threadless including cutting stem).
Purely in terms of cost, it will cost you more than 100£ in tools and effort. However if you plan to work on bikes longer term it is worth it.
You will need a crank puller, hex wrenches, bottom bracket tool adjustable wrench (potentially a cheater bar as well), headset cup remover (bear in mind there are different sizes), plus probably some oils, lubricants etc
It isn’t massively hard but will take you time. If you plan to do this kind of thing more than once or twice, I strongly recommend doing so because it’s super fun