I've been wiring cars and boats from scratch for more than 50 years and even I don't do it that way any more. By the time you buy all the components it is just as cost effective to buy a kit, plus the wires in the kits are all labelled as to where they go, making it so much easier.
I have installed American Autowire, Rebel, Painless, and Ron Francis kits. IMO there is no better kit than American Autowire, but they are NOT CHEAP. I honestly feel that for the money a Rebel Kit is a good value. I installed one in my 27 and will install one in my latest rpu project when the time comes. The AA kit has the advantage of each wire individually being removable from the fuse block, which does make it simpler to install, but what I did with the Rebel kit was I cut all the unnecessary wires off the fuse block before I installed it and only used the ones I did need. (my car doesn't have AC, stereo, 3rd brake light, etc, so those wires were just in the way)
With any kit you will still have to buy quite a few extras, like switches, wire ties, terminal ends, shrink tubing, etc., but aside from that they are pretty complete.
Also, some people like to solder and some like to crimp........I crimp because I work in the marine industry and there are a lot of reasons why boats are only allowed to have crimped terminals, and in my experience, crimped holds up just as well if properly done.
Don