Hi @DemaonProf ,
This is Ellie from BOGOS (formerly Free Gifts by Secomapp), #1 Promotion App on Shopify.
Here are my recommendations. As of my experience, these are easy to use apps but they still provide you with powerful features so they might fit your needs:
- Recharge Subscription: intuitive interface, various subscription models with great support center
- Subify Subscriptions: clean design, focusing on essential features
- Ongoing Subscriptions: user-friendly interface, a straightforward subscription app
If my answer is helpful, I would appreciate it if you could give me a Like or accept it as a Solution! 
Wish you all the best with the business,
Ellie
BOGOS (formally Free Gifts by Secomapp)