what apps are good to manage with free theme until finances allow booster theme?

Thank You Rito for all the value in your bizathon videos. They are very informative.

I’m running my store on shopify by following your Bizathon videos. I currently don’t have the money to purchase booster theme. Could you tell me apart from countdown timer, what are some great apps which you think are best to manage with on a monthly basis. My bugget is around 50$/month as of now.