This is a collection of training maps that provide great functionality and have helped me personally improve my CSGO skills. None of these maps is made by me, all credit and props go to the creators of the maps.

The list starts with a bunch of aim-focused maps same train a lot of things, others only a single aspect but very well.
Further on in the list you will find sound training, config helpers and even a surf map that may get you started with surfing.

You surely won't be able to use all maps but you should be able to find a couple of them that you like so you can incorporate them in your warmup/training routine.

The linked collection is by a guy named Yesper who does some of the highest quality custom maps out there for training. You'll find a training map for every map in the active map pool. These maps will get you started with nades (although some lineups are maybe not ideal), prefire spots and peeking. The prefire mode is a great tool, to get your aim going as well.
Additionally he has some aim and recoil training maps that provide similar functionality to the ones put in the collection, so give them a try as well!

Cheers!