Ask HN: What web service categories should I be thinking about?

I am developing a subscription based B2C Web app and I am a bit overwhelmed at all of the different business services out there (Salesforce, Hubspot, BrainTree, MailChimp, etc.)

Can someone please help my wrap my brain around what kinds of tools I should be looking into and maybe provide a few recommendations of specific providers?

At the moment I am thinking I need: - B2C CRM - Email Marketing - Payment Processing - Analytics - Accounting

Are those the basics or am I missing something?