I'm going to talk about the mechanics tools, the range of woodworking, electronic, building trades, machinist, gunsmithing, jewelry and other tools is too wide to discuss.
I'm going to change the rules; I have as close to nothing invested in my tools as you can get. I picked up most all of them a piece at a time for pennies at yard sales, bought large boxes full of stuff, sold most and kept the profits in the best tools, put together sets and traded up to matched stuff that I wanted, etc. It's been a lot of fun doing it; it's something I enjoy. So, if I got out of my tools what I've invested in them, it'd be the loss of a lot of effort I've put into them over the years, and no cash.
If I got out of my tools what they were worth, and had that to invest back into them, I'd go to Proto and Snap-on and buy a comprehensive, basic setup:
Snap on ratcheting screwdriver, and 3 phillips and about 5 flat sizes fixed blades.
Snap-on full range of torx drivers.
Snap on 1/4" drive, regular and deep, metric and SAE sets.
Snap on 1/4" flex sockets, up to 12mm and 1/2".
Snap on 3/8" flex sockets, from 12-17mm and 1/2" to 3/4".
Proto 3/8 and 1/2" drive sockets, full range of sizes, regular and deep, 6 and 12 point; up to about 24mm and up to 1 1/4".
Proto 1/2" drive impact sockets in SAE and Metric
I'd purchase 1/4" Snap on ratchets, regular and flex.
I'd purchase a full range of breaker bars from Snap-on.
In 3/8" ratchets, I'd deviate from my new Snap-on and Proto mode, I might buy a few Snap on, but I'd look for my favorites, which are old Indestro. I have well over 20 ratchets now, I'd aim for about 15 that I really like.
About 30 extensions from 1" through 18" long, all 3 drive sizes.
Snap on mini combination wrench sets in SAE and metric.
Snap on short combination wrench sets in SAE and metric.
Snap on Long pattern wrench sets in SAE and metric, through 1 1/8" and through 24mm.
One set of long pattern Snap-on double box wrenches in SAE and Metric
One set of short pattern Snap-on double box wrenches in SAE and Metric
Two of each size Proto adjustable wrenches from 6" through 24".
Two of each size channellock slip joint pliers.
Full range of Snap-on needlenose, duckbill, end cutters, side cutters, etc in small pliers.
Complementary range of Knipex pliers for what Snap-on doesn't sell.
Full set of Snap-on Torx and hex key sockets, in 1/4 through 1/2" drive.
Wide range of Proto Universal pullers and gear pullers.
Wide range of ball pien, cross pien, deadblow, plastic faced, brass, and other hammers. I use about 20 different ones overall.
One comprehensive Snap-on chisel and punch set.
One rull range Snap-on spiral extractor set.
Snap-on Tap and Die Sets in metric and US.
IR impact driver, 1/2".
Snap-on hand impact driver set and bits.
From here on, I'd buy things as they occurred to me that I need them, in the brand that I like the features best.
The two things that I have now, that I would think about not re-buying are:
Proto 3/4" drive socket set, SAE through 2 1/2 and Metric through 55mm. Matching ratchet, extensions, etc.
One set of Proto combination wrenches from 1/4" through 2 1/4".
I use some of this big stuff, just not all. I might expand my 1/2" drive socket set to 1 1/2" and my SAE wrench sets in the "basic set" above to 1 1/2" to eliminate the need to buy these two sets I have now. And then, buy the individual larger tools only if I have a need for them specifically.
The notable absences I have in my list above that many of the guys here consider essential are ratcheting wrenches (have some, have had a lot, didn't use them so sold them) and extensive air/impact tools.
I have been paring down my mechanics tools a lot over the past 3 years, and upgrading to exactly what I want. What I described above covers probably 1/3 to 1/2 of my mechanics tools. The other 1/2 to 2/3 is in danger of me excessing them in the future.