Start with estimating and invoicing in one place. The gap between quoting a job and invoicing it is where trades businesses lose money, through work quoted from memory, change orders never captured, and invoices sent weeks late because the paperwork accumulated. Software that turns an accepted estimate directly into an invoice, from a phone, on site, removes the delay and the retyping. Getting paid faster is worth more to a first year trades business than almost any other improvement available.
Scheduling and dispatch matter as soon as there is more than one person or more than one job a day. What you need is visibility of who is where, the ability to move something without a phone call, and the customer being told automatically. The last part is what generates the reviews, because a substantial share of complaints in trades are about communication rather than workmanship, and an automatic message saying somebody is on the way resolves most of it.
Photograph everything, before and after, on every job. This serves three purposes simultaneously and businesses usually only think of one. It is your evidence when a customer disputes what was there before you arrived. It is the material for your website and your listing, which for trades is what actually persuades. And it is the record that lets you answer a question about a job you did eighteen months ago without visiting the site.
Payments should be accepted in the field rather than invoiced afterward wherever the job type allows. A card reader connected to your invoicing software collects at the moment the customer is most willing, which is standing in front of finished work, and it eliminates the collection problem entirely for those jobs. For larger projects, deposits and staged payments serve the same function.
The one that gets neglected is the customer record. Knowing what you did for somebody, when, and with what parts, is what makes repeat work and maintenance contracts possible, and it is the difference between a business that starts each year from zero and one that has a base. That record can live in your job software rather than in a separate system, provided somebody actually fills it in.