The warmup is essential for CSGO before you head for matchmaking or any game, essentially you must do a warm-up, it helps a lot, especially to improve your aim and reflexes, So for you, I have selected the 2 best Workshop maps for warmup, which will help you a lot to get ready for your matches, and improving your accuracy, and reflexes.
1) FAST AIM/REFLEX MAP – TRAINING [DUST2]

This map by cr0coDiL is a map which will help you practice your reflex movements, in the map you are placed in the middle, and bots come to you, and you have to kill them before they fall into the pit. The map has a lot of settings, but I think the default is the best. You can try all types of weapons in this map.
The unique thing about this map is that you can change the speed of gameplay (increase/decrease), as you can see in the video below.
You can subscribe to the map from here : https://steamcommunity.com/sharedfiles/filedetails/?id=647772108
2) Yprac Bot Arena
This map is by the one and only Yesber who has made some great workshop maps for practice. You can also check out his other maps which are great for practicing different maps, but the one to practice your aim, reflexes, and do warmup is the Yprac Bot Arena.
As soon as you load the map you are greeted with an amazing menu, then to start you get on the ramp and start shooting bots, the unique feature of this map is that you can see your KPM score as you shoot bots, your aim should be to increase it with time.


After shooting the first 50 bots, you are also presented with the final score, which you can keep it as a refrence to improve upon, there is a lot to this workshop map, which you will notice one you will try.

You can subscribe to this workshop map from here : https://steamcommunity.com/sharedfiles/filedetails/?id=1104441
So these were the 2 maps which I find are the best ones for warmup, what do you think about them? Do let us know in the comments.