Complexity of IoT with web UI

One of my on going projects collects data from IoT sensors and displays them on a web page. The things I had to learn were quite a lot. Here is a short list:

1. VPS, Ubuntu, Putty, Filezilla
2. Nodejs, Javascript, HTML, CSS, socket.io
3. Arduino IDE, libraries for sensor, board etc.
4. Sending data from sensor to VPS
5. Custom hardware design for rugged case, smaller form factor and minimal power consumption (done by a friend of mine).
6. Obtaining a domain name and redirecting it to VPS IP
7. Nginx as a reverse proxy
8. HTTPS, certification
9. Login, register
10. Online payment
11. Database