You may use Hostgator to send emails from your own domain but deliverability rates with be a fraction of what professional autoresponder like Aweber has.
In other words out of 100 emails you sent out to sell your services, 20-25-40% will end up in a spam folders of people without them or you knowing it. This is just a fact of modern anti-spam war live. To avoid that - people use professional autoresponders, like Aweber.
If you start now without autoresponder and notice that your business suffer because part of your emails are lost - you may decide to switch to Aweber later on and import your existing mailing list. The problem you'll be facing is that Aweber will require all people to be double-opt-in again. Which means half or more of existing emails in your database will still be lost, as many people will ignore double-opt-in request after the fact.
If you are launching just fun blog website - you don't need aweber.
If you are launching online business and plan to grow it - include Aweber part now as making this shortcut now will save you money now but will hurt you more later.
Each line in my todo list posted a bit back is carrying lots of personal and professional experience.