Adobe beginner

I would recommend not going with Xd. Xd is new so there is not as much documentation/online support. Also, many of the features are not in their "final" state and may change over time. The experience is significantly different from other Adobe products so the skills you learn for Xd will not exactly transfer as you move on to the more professional tools.

Personally - I started with Photoshop CS2 about 15 years ago and I would recommend the same for a beginner today. Photoshop is (arguably) the most advanced app but also the most fundamental Adobe program - the concepts are prevalent throughout almost every tool in the CC suite.

Don't get overwhelmed by how much you can do within the app. Find a good tutorial to create something that seems interesting to you and just focus on the capabilities within that one project. Then build from there. There's no need to master 100% of the app's functionality when you will use 10% of the features 90% of the time.

Illustrator was the second app I learned after PS and (for me at least) I'm glad I didn't have to learn the program mechanics at the same time as vector graphics conceptually. At first I found the vector format frustrating and limiting compared to raster graphics (ie Photoshop), so I'm glad I had a baseline understanding of navigating Adobe apps going into it. Now, Illustrator is my go to even for things that could be easier done in PS, but I'm glad I had the foundation in PS before starting.

I would classify Photoshop, Illustrator, After Effects and Premiere as the 'big 4', and all the other apps are just expansions or refinements of the basics established within those 4. If you want to eventually be comfortable in the whole suite, starting with Photoshop is the smartest use of your time I can recommend without knowing more about your background/interests.

Here is how I would explain the primary purpose of each of the big four in extremely basic terms (if you're not familiar with the difference between raster and vector graphics, that is something you should understand before deciding):

1. Photoshop -  the godfather of creating and editing raster based 2D graphics
2. Illustrator - the godfather of creating and editing vector based 2D graphics
3. After Effects - video compositing program for integrating computer generated imagery with video footage
4. Premiere - fully capable video editing program for cutting and arranging footage

What are you trying to learn/become?