To get useful advice, you need to give potential advisors a more-detailed picture of your background (mostly how much you know about electronics in general, and microprocessors in particular), and what sorts of things you want to do with an Arduino/other board. E.g., there are many "Arduinistas" who have a lot of experience writing PC software, but know little/nothing about hardware, and got started with the Arduino to learn about "low-level" programming and hardware. Some are electronics experts who want to learn about software. Some are artists who know nothing about hardware or software, and just want to learn a minimum so they can make their sculptures move, or their stage lights blink in fancy ways. Each person has different needs.
I know that Lady Ada has some kits oriented toward specific areas, like motor control and analog measurement. However, while I generally like and recommend her products, I'm not too thrilled with her motor controller: it's well-made, a good deal on price, and exceptionally well documented, but it uses up a lot of the Arduino's pins. If motor control is on your list, get some suggestions from people who've used controllers like those from Pololu that use fewer pins and/or can run very heavy-duty motors.