My approach, and I think it has been a good one, is to buy a decent socker and combination wrench set (Crafstman, Husky, and a few others offer plenty of quality for a shadetree mechanic, in my opinion) and work from there. I haven't bought that many more tools beyond that, partly because I've been able to borrow things that I only rarely need. I spent $70 on a high-quality tie rod tool several years back and haven't regretted it. Some non-standard tools are worth the extra cost to own, it just depends on what you're doing. Oh, and I've gotten by just find with Haynes on our vehicles; I wasn't too impressed with the Chilton manual we got for the Volvo we had several years back. A FSM is no doubt a great asset though.

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Once and future king:
'64 Ford Fairlane w/approx 238,000 - looks rough, but amazingly reliable if you know how to look after it; I will soon begin work to totally restore and modernize it.
Family vehicles that I lay some claim to:
'78 300D w/approx 350,000 original, '62 Ford F100 4x4, '90 Ford E150 w/171,000 original