Welcome to Constant Contact @AnnetteT14 , we're happy to have you trial our systems. If a sales agent sent you an email, you should be able to reply directly to their initial reachout email to get connected with them. However, we're happy to answer any general questions or support inquiries here in the Community.
For different topics that you'd send emails out on, you can setup separate lists, as well as sign up forms and update info forms, for contacts to select what they want to receive emails of. Generally the best form option is going to be a simple Landing Page sign-up form (with a URL that can be effectively pasted anywhere other links can) for collecting new signees, as well as ones you already have updating their info. Other options include the Update Profile form you can include in your email footers. We also have inline and pop-up forms available if you'd like one hard-coded into your website.
Automated birthday emails are available for creation and scheduling. Such emails can be scheduled for the day of, or up to 14 days before.
At 300 contacts, you'd be in the 0-500 contact tier which runs at 20 USD per month for the Email plan, and 45 USD per month for the Email Plus plan. I'd recommend checking out the Pricing Comparison page on our main website, or the Plans & Pricing page in your account, for a full breakdown of features and costs at different contact tiers. If you have other general questions regarding Billing, you're welcome to check out our Community's Billing FAQ, which also acts as a nexus to various useful billing-related articles in our Knowledge Base.
If you have any other general support questions before getting started / transitioned to a paid account, feel free to respond in this thread, or create new threads for those questions. We also have several other support channels available.