Its very easy to create a blog. Write your experience or experties. More content you write, more it comes in search engine.
Google Stories
Find some interesting topic and create google stories. Integrate AdSense easily and make some money.
Youtube Channel
You just need a camera and time. Shoot anything you like and upload in youtube. Internet is very interesting place where anything goes viral! More views, more ad, more money
Develop Mobile App
Everyone has mobile. If you can make a app which solve a problem or make people engaged there is chance you are showing more ad and make more money.
Publish eBook
It may require little effort but if you can make some there is high chance you will get royalty from the book for lifetime.
Web Design
Every business goes in internet and they need a website for presence in internet. If you can design website for company and you will end up with some money. Try freelancing sites.
These all ideas requires no or very less investment to start. You just need patience and time. Success can't be got overnight
Advertisement can work in traffic. More content you generate, probability of traffic will increse and that increase your earning potential.