By all means get yourself a CT-3.x chain tool, and the Shimano cassette lockring tool (FR-5.2). I suspect the 5.2G can be made to work with 12 mm through axles, if you have those, but I haven't personally verified that. The big CT-3 is worth having in your toolbox over the dinky little versions. I've done fine with regular pliers to get quick links off, so I don't think chain pliers are required. A good cable cutter is great, although you can get by with a Dremel cutoff wheel.

Think about what you'll need to fix common problems on the road. Each of my bikes has a seat bag with a spare tube, patch kit, tire levers, and multi-tool. Add your choice of either inflator and CO2 cartridges or a pump. (Note my flat tire kit gets a lot more use than the multi-tool.)

For the rest, wait until you need a tool to buy it. Steel bike with integrated derailer hanger? Might want a derailer alignment gauge. Wheels breaking spokes and/or going out of true? Load up with appropriate size spoke wrench, truing stand, and tensiometer. Unless you buy the Park catalog, there's always going to be a tool you didn't think of; and if you do buy one of everything, you're going to be sitting on a bunch of unused, expensive tools.