Adobe Brackets - my personal choice and it is a free code editor which is really user friendly and perfect for beginners. Simplicity is what I love about Adobe Brackets and if you want add more functionality, you can install extensions and customize it by their wide range of themes. It has auto-complete feature and live preview. The space it will took in you hard disk is reasonable but it will not eat more than 1GB of your hard drive.
Same thing with Atom editor but the thing is, it tends to get slower and performance wise, Atom might only be second in my choice but it is true that it is more popular than Adobe Brackets. Atom has Git and Github integration as well. Sublime is the third (never tried it yet) and last is Visual Studio Code.