Initially, we sold individual routines. There's almost no money to be made on the app store that way (especially with Apple taking 30%). To actually build a business - we switched to a subscription based service and it made a huge difference.
i think that's a very good idea. it's the same thing the guys at Scentbird did, that was when they finally started making money, from subscription.
Do you provide trial for people? maybe 3 - 14 days, that may help.
Also, you may try marketing too, i think it's much easier for people to instal apps they see on Facebook Ads.
I like the subscription model, once i find a good product/market fit, i'll start looking into that.