Where do I start?
The most common place to start with email marketing is a newsletter. The best way to maximise your efforts is to understand your customer, your capabilities and your goals.
What does your audience want to hear about from you? Is it interior tips, project stories, your opinions on the industry, identify what it is that they value from you. Not sure what they want? You can ask your followers through social media, in person or via a survey. Once you've identified this, you can start calculating how long it would take to produce that content.
If you want to send a newsletter, it needs to happen regularly enough that the customer can look forward to expecting it in their inbox. Ask yourself how much time you can dedicate to this content consistently. Does it mean writing blog articles, curating project imagery, collating press clippings? Starting with a monthly newsletter is a good idea. You can scale up its regularity should you find you have more time for content creation along with a positive response to your mail outs.
Also, what do you want to get out of the marketing? Increased follower numbers, industry recognition, new clients? Whatever the goal you need to hone on what will help you to achieve this. Interior tips and tricks could boost your readership and brand, but not your client base. Whereas project stories may help with the latter, it all depends on this mix of considerations.