AppStore - $0.99
This is a software gives your Mac the AeroSnap-feature from Windows 7 but also add tons more features and shortcuts to enhance your workflow. Ever since I started to use MacOS full-time, a tiling window snap-software has always been the first thing I've installed.
https://www.smoothscroll.net/mac/ - $19.95/yearly ($9.97 when on sale)
If you're using a regular mouse and not a trackpad, you'll notice that the scrolling hasn't been updated since the last decade and is a bit choppy because Apple believe trackpad is the best way to use MacOS. If you're like me who still prefer using a mouse, then this software will make all scrolling just as smooth as the Apple trackpad everywhere. It's especially great for a Logitech mice which you can disable the click-scrolling.
https://www.macbartender.com/ - $15.00
Bartender lets you hide and organise your menu bar icons very easily and its useful to make a less cluttered menu bar especially on a small screen laptop such as the 12" Macbook. I use it as a secondary menu bar for software that mostly runs in the background such as SmoothScroll, Magnet, Dropbox, GoogleDrive Sync etc.
AppStore - $7.99
This app creates a drag-n-drop area, a basket for files you want to drag and drop between software, or save for later. The workflow in MacOS is to; drag and hold files to your app-icon, wait a little, select your window, wait a little and then drop your files. This becomes a bit cumbersome after a couple of times and if you accidentally drop files during the window-select animations, you have to redo it. This app is perfecting the drag-and-drop user experience that Apple originally intended to design.
AppStore - Free
MacOS has a very limited set of options for sleep/wake in system preferences. Sleep/Wake is an important function for laptops and not all software tells the computer not go to sleep when you watch a video etc. It's mostly an issue which exist for cross-platform software. Amphetamine makes it easy to take control with a simple menu bar icon, set specific settings depending on the software you use, or even specific devices etc.