Lister, it's a long time since I flew a taildragger, and mostly it was rather heavier ones than your Cub.
Choxolate gives some good numbers. To add a little to that, recheck your POH. It should tell you fairly explicitly the limits for the gusts allowed for. Beyond that, I would (personally) increase my IAS by all the increase in gust factor.
Say the POH allows for gusts up to 15 kts. If the wind is gusting 20 kts, I would add a further 5 kts on top of what you've already added.