I am currently on my way to creating an online course. The problems that I'm trying to solve are: 1. Getting additional money from freelancing jobs as a programmer 2. Difficulties on learning to program 3. Getting clients It's for Ruby on Rails programming at the start, but once this succeed I want to branch into other programming like React, Python-Django and Node.js. Probably the target market is people who already have a job and want to switch careers into IT/programming, people who want to get additional income from freelancing, people that want to get dollar online (my target country is not USA), or perhaps start up founders who want to learn to code. I'm still clueless on how to market this course once it completed.
You seem rather undecided on important factors that will affect the outcome of any marketing plan. Rather than provide you with marketing advice, I'll provide you with the information you need to conduct proper research so you can make informed decisions when it comes time to market.
According to Entrepreneur.com, research is the step people who want to start a business skip often. They either assume they have all the necessary information to go forward, or they think they lack the time and money to be thorough and go forward anyway.
But with only a fraction of new businesses surviving their first year, you don't want something as preventable as "I don't know" to be the thing that does you in. So start with research.
You can get primary research (info direct from customer base) from social media platforms, forums, other network sites, and local spots (schools?) where you know people interested in learning about programming tend to gather and talk about their circumstances, needs, likes and dislikes about the current market options, etc.
You can get secondary research (info from research entities on your market) from sources like MarketResearch.com, which has reports in every industry searchable by country. There are many others, including research reports available from corporations in your industry.
You'll know you have enough information to decide how to market when you can build a detailed profile of the person most likely to register for your course, list some of your nearest competitors and their strengths and weaknesses, and have at least a general understanding of market trends for online courses like yours.
As you go, you'll find certain pieces of the marketing plan will fall into place intuitively. Others you might still need some assistance with. I'd be happy to talk with you again at that time.