If you’re planning to launch a new site it helps to have 2GB of memory instead of just one, otherwise you may have difficulty updating the app through the web interface or even command line rebuilds sometimes fail with error 137 for not enough memory at only 1GB. Adding more swap can help.
The documentation still reads that 1GB is good for minor communities, but they might want to change that to 2 one day unless app is refined to work better with less memory. Have read there have been some significant changes to the core system over the past year or so.
2 GB memory servers are typically about 12-14$ u.s.d. per month, double 1GB server which can be $6 or less a month.
For e-mail sending mailgun still has a free/flex plan for less than 1,000 e-mails a month, but they aren’t really advertising that to sign up for a new account with them is $35 a month standard, but then you can contact support to downgrade to free account that won’t charge you unless you go past the 1k e-mails a month threshold.
Other e-mail senders may be better, one I use is Proton Mail for $13 a month business plan is compatible with discourse but that may not be recommended or supported.