I was new to bikes too, although I had a few years experience with older cars.
It really shouldn't be too much if you just get the essentials. I had to start from scratch almost on the tools because I didn't have a single metric tool in my box.
You may want to check on the "mechanic sets" they have at sears, I'd strongly recommend sears because of the ease of return if you do break one.
I got so far:
9 piece metric box ends, 19.99 on sale
Impact driver, you gotta have this! 24.99
Metric socket set, 30 - 40$?
18mm deep socket, for spark plugs
Magnet pen, it's handy
Feeler guages
Voltmeter - 5$ at Harbor Freight
plus I had...
Adjustable wrench, 250mm
+ small adjustable wrench
Vice grip - use sparingly, but you'll need one
Rubber mallet
Screw drivers, asst. sizes
All that'll set you back about 150 - 170$, and most anything you'll need beyond those will be task specific tools. I may be forgetting something obvious though...
Good advice from everyone so far, the board has been a butt saver a few times for me already.