What are the best way to build my company list and gather information for data analysis?

I would suggest Web data extraction, it is one of the best way to collect targeted information from your competitor's website and entire web. You can easily track numerous website for gathering information for your business.
You can scrape data from Craiglist , GumTree, Yellowpages and other classified and business directories to build your list.

I think in such issue business analysis experts from business analytics course provider as “ExcelR Solutions” can help you the better way, so make a contact with them.

You can get all company list database of more than 30 countries with full contact details at https://emailnphonelist.com/

Graeme Newell and his team at 602 Communication work as the best CSR consultants, working over every component of corporate social responsibility, empotional marketing and market research to increase customer base, employee engagement and boost profits.
http://602communications.com/