Starting in circuity, Should I use Arduino?
It depends on what your true goal is, to really learn about microcontrollers or to get a few projects done.

If you just want to get something done without too much having to know what is really going on, then a arduino or some other development kit like that is a good choice.  These put a lot of infrastructure around the micro and dress it up with layered constructs so that you can get basic things done without a large learning investment.  The downside is that all that abstraction obscures the lower levels, so this is not a good way to go if your aim is to understand those lower levels and what goes on under the hood.  They also of course cost more than a bare micro, although even with a bare micro you'd have to provide some of the infrastructure yourself.  Microchip has come out with a arduino compatible board that uses a PIC 32 under the hood.  I forget the exact name, but from the little I've looked at it, it appears to be a good value and has better performance than traditional arduinos that use Atmel processors under the hood.

If you want to really learn microcontrollers, then there is no substitute for getting into the low levels yourself.  This will take more investment to learn, but in the end you'll be able to do a lot more with the same chip than what the abstraction layers of the sugar coated arduino-like products give you access to.  If this appeals to you, then start with a simpler microcontroller and do a few projects in assembler.  In this mode, even just a compiler becomes a obsuring layer between you and what you want to learn.  This is not to say eventual projects can't be done with a compiler, but that you need some assembler experience to really appreciate what is going on and the issues the compiler faces on your behalf.  Since you're not looking to do volume products, it doesn't matter whether the micro costs $5 or $1.  I am most familiar with Microchip's offerings, and from their product line I'd stick to the 24 bit core varieties.  In particular, I'd start with a small 33F part, but the 24, 30, and 33 series are all the same instruction set.  The C30 compiler for these is quite good, unlike the compiler for some of the other PICs.  The compiler's calling and stack conventions makes sense (again, unlike with some other PICs), and it's easy to write assembler routines that are callable from C30.

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