My clients and sales calls, and my own experiences and struggles.
The easiest thing to do for content is to think about what questions your clients are asking, or what they need to believe, and then answer them.
ChatGPT (if used well) is also a goldmine for content ideas.
Depends on the size of your business and your clients. I use a mix.
Close is a great CRM especially for sales and pipeline - I feel like you could use it for the asset tracking too
Dubsado if you're smaller could be an option too.