I'd frankly just play with it for a while. There are no real tricks needed to learn to read ASCII, especially not the "High ASCII" (CP347) graphics, with both foreground and background colors, used by Dwarf Fortress as opposed to the standard ASCII used by, say, Nethack (which I play with the standard tileset: no confusing one h for another).
You may or may not lose an early fort due to misplay, but by the time you do, the ASCII will create as much a picture for you as the graphic packs. I've never used a graphics pack, but from looking at graphics pack screenshots, the ASCII is actually a lot... cleaner. even with Varied Ground Tiles and no flow amounts. When reading succession forts, I get more information at a glance from ASCII shots, especially about which dwarf is which. ☺ and ☺ look more immediately distinct for me than most ways a tileset differentiates "mechanic" from "mason" for instance. You may think this is natural, as I've used only the ASCII and not any of the common graphics packs, but the goal of a graphics pack is to make the screen more readable than ASCII at all times. I don't... I don't particularly know if its possible, frankly, especially now that procedurally generated creatures like FBs and Titans are just going to make graphics packs throw up their hands and display ? or the normal tile rather than trying to figure out how to render every possible gigantic blob composed of slade with wings of stretched skin, one-eyed mandible-bearing therapod with pink feathers, and monarch butterfly twisted into humanoid form on the fly.