http://www.homedepot.com/p/Dia...
http://www.lowes.com/pd_27179-...
https://www.amazon.com/dp/B000BMBPGU/
The porter cable is one we've had good luck with (the one linked from Lowes...and Amazon has them, too).
I'd start with a pruning blade...it's pretty aggressive. Then, if you want finer cuts or are cutting fibrous stuff, any assortment would do. I think you might be happier with the longer blades (9 inch), generally, than the shorter (6 inch), though. I found an assortment box of 30 or so of them at Costco a while back for twenty dollars.
Here's a random assortment from Home Depot -
https://www.amazon.com/dp/B000BMBPGU/
Hard to know what exactly to recommend. I'd try the pruner first...then if you want other blades, get an assortment that has a broad spectrum of teeth-per-inch (tpi)- from 6 to 24 or something...and then figure out which ones are most useful to you...and then buy replacements for the specifically useful ones as you dull the originals.
