First, congrats! Buying a business is not an easy task.
Before anything else, I would sit down with all the employees (together and separately) and hear from them what are the problems in the business and what they think should be the priority.
This will have 2 affects.
1. They will respect you for giving them a voice.
2. You will get smarter by the minute on what the business needs.
After that, before anything else I would just set up systems in place, processes and systems are super important when you run a time and materials business.
Understanding the cost and getting the cost of goods and labor down would be my first priority. Processes will help with that since less time will be lost.
Systems I would put (in order of priority)
1. Orders and production
2. CRM *customer service, customer relations, sales and more should be included to make sure you maximize your business.
Without more details it's hard to give more tips, but depending on the business type a website with online orders and online quotes can go a long way, for other types it's not that important.
Above all, good luck with your journey and your business. Take care of your employees, they will take care of you a lot more in return.
If there's a single tip I can give you is to treat your employees as equals, as you want yourself to be treated, they are your single most valuable asset.