Julie here from Shopify Support.
First off, congratulations on opening your store! Before launching, did you get a chance to review our "Essential Shopify Store Launch Checklist"? This is an excellent resource that'll help you ensure you've completed all the necessary steps before you start selling.
In regards to which apps you should be using, this totally depends on what you need the apps for. Based on the title of your forum post, it looks like you may be searching for apps to help with shipping and collecting taxes. Is there a reason why you're considering an app for this? Are there any specific features that you want to add to your store that aren't available in our built-in tax settings and shipping settings?
For some examples of our most popular apps, I recommend checking out our blog post, "25 Free Shopify Apps to Check Out In the Shopify App Store". There, you'll find a list of our most popular free apps, along with some information on each one. For more ideas, I also recommend browsing the Shopify App Store, where you can browse apps by category (like Shipping and Taxes) and view trending and popular apps.
I'd love to hear more about the types of features you're looking to add to your store and which apps you're considering! Feel free to respond here and let me know; based on your specific needs, I'd be happy to share some options with you.