Johnny, if you like blues (as per your OP) and want to be able to improvise over blues backing tracks, you only need to learn one scale, the blues scale. Learn that scale backwards, and at the same time, learn your favourite blues solo's by ear as Jeremy suggests. Just start with one note, two notes, a short lick..as your ear develops it'll all get easier. You could argue that if you learn the solo's, you'd don't even need to care about what the scale is..but I think it helps to "see" the framework for the solo in the long run.