For 13 x 19, a reasonably newbie-friendly approach is to buy 22 x 28 frames, plus a 22 x 28 matte with a 12.5 x 18.5 cutout. Gives a big, even, 4.5" matte all the way around the image that will make that little print look a lot bigger.
These guys have those kinds of pre-cut mattes for too much money...http://www.lightimpressionsdirect.com/westminster-pre-cut-mats-black-22x28-13x19-5-pkg/hinged-exhibition-mats/
You can cut mattes yourself, but if you want to cut mattes buy a decent matte cutter without the name Logan on it.
Amazon overfloweth with 22 x 28 frames. Learn how to cut glass, buy some hinges, pick up a cheap version of the Fletcher "point gun" and yer good to go! Oh, if you use that manual point gun enough, you'll have degenerative hand diseases by age 50, no problem. Get a pneumatic model if you're serious. Point guns shoot flat nails to hold the matte and glass in the frame.
But personally I print mostly canvas, glue it to Gator, and frame it minus glass or plex or matte. So easy, so lucrative.