More strength, more agility.
You pretty much won't ever get sacks until you have speed around 43-44...that is the critical number to actually have a hope of getting to the QB.
You'll want more speed eventually...a lot more. But that gets you in the zone at least.
I'll repeat, more strength, more agility.
Many folks will tell you to stop building a strength based DE...you don't need to listen to them, they work fine. They won't give you crazy sack numbers, but they will give you some quality sacks, and they can help your team tremendously.