Making $200 per day is pretty tough when you just have started your business with WordPress, but it is possible if you have some patience and work on your skills and reputation, so that you get the right clients.

For starters, you can start to build more skills by offering your expertise on project platforms like UpWork.com. I have done this and got a bunch of good clients who paid me for larger projects over time. But it took me about a year to get to a point where it was starting to be profitable. On the other hand, I have learned a lot about getting new clients, working with clients and handle difficult clients. So I think it's worth a try.

After a while, I took on work on codeable which ist much better to get clients who are willing to pay more for excellent solutions, but I believe you need to get invited there, so you have to build some kind of reputation in WordPress first, to show that you are a top coder.
Referring to your question if it's better to get many small clients or a few large ones, I would aim for the larger ones as getting on a new project will take more time in just getting started with the client (like understanding their needs, exchanging all necessary data like login passwords, etc).

From my experience, it's also great to have agencies as clients, who are doing websites for their clients. I worked with a lot of designers who used me just for the coding part, so I've got a lot of smaller projects but all based on the same design agency.

Hope that helps.

Let me know if you have any questions.
Marian