It's simply an idea to make someone else's life better - Richard Branson
Domain names you can get from any registar. I recommend GODADDY simply because they play nice with other platform. For example with Leadpages when you use GODADDY Leadpages has an automatic link to connect domain and website. So you don't have any technical work to do that you may not be familiar with. Other Domain registars you with be required to set the CNAME and A-Records.
Gmail has a professional business email service (Business Email meaning it ends with @~yourdomainname~.co.uk not @gmail.com). Before you set this up, you'll need to have a website (Not finished, but a holding page saying coming soon would be a good start). You need to launch a website first as you'll be asked to prove you are the owner of the domain name associated with the business email as part of the setup process.
One mistake I often see is businesses owners driving traffic to their website by using online tactics such as being active on social media, maybe a short stint using Pay Per Click advertising. However, the result is customers are landing on the website, but still not taking action. So we have a web conversion issue, turning those visitors into enquiries for your services or even better-paying customers.
Relationships = Interactions over time. So you’re going to build a stronger relationship with somebody the more interactions you have with them over a longer period of time. This is how trust is gained. Don’t build a relationship and you'll fall back into a ocean of competition where the consumers decision-making process comes down to price and you will be working with customers that are not a good fit for your business.
As a Sole Trader with no-one to turn too, I started off making money doing what I enjoy with no business knowledge. I always struggled with accounts and every year I tried a new software. After 4/5 years testing several platorms, I finally found Free Agent that displays everything in a simplified way and in real time. No concern of scary tax bills! I know everything financially in my business. As a Sole Trader you can submit your accounts direct to HMRC. I pay a small fee to an Accountant to glance over my books before submission. FYI: The support team at Free Agent are accountants and not software developers so you have plenty of help and advice.