For email marketing and customer relationship management software, Aaron recommends:
Beginner: Mail Chimp (https://mailchimp.com/) - if you're just starting out and have no background in technology or automation this is a good choice. Though you may not be able to tag people and move them in and out of sequences, you may never need to do that.
Intermediate: Drip (https://www.drip.co/) - Drip is getting a lot of momentum, they have a very simple, very affordable automation platform that can accomplish a lot of advance automation tasks.
or Active Campaign (https://www.activecampaign.com/)
Advanced: Infusionsoft (https://www.infusionsoft.com/). Aaron uses Infusionsoft - if you want to have a good toolkit in place, and you can afford $250-$500 a month because you already have a large enough list (5,000-10,000 people) then you can monetize the list and Infusionsoft may be a valuable tool for your business.