Don't pick an iron set based on your handicap. You should pick them based on what you want to get out of golf and of your irons. If you're a reasonable ball striker, you're quite capable of playing blades or other so-called better-players' irons.
On the other hand, if you're not a great ball striker, or have a fade you want your irons to correct, or not confident, or just plain want the extra forgiveness, there are plenty of good cavity back sets out there.
In fact, you can mix them if you're in between. The AP1 and AP2s, for example, are designed to be mixed. Maybe you want 7-iron and down to be players' irons, but want the forgiveness in the rest (without resorting to hybrids). Then you might consider getting AP1s for 4-6, AP2 7-W.
Brian Gay won a tournament not too long ago with a mixed set that included blades for 9,P and Super Game Improvement irons for 3,4. I think he won two tournaments with this configuration, by a combined total of 15 strokes. His were Mizuno irons, not Titleist irons, but the idea remains.