I once shared that enthusiasm, but then I looked at all the stuff you had to do and you'll regret ever getting into mapping :D.

There are plenty of guides on the webs that explain dozens of different items you will apply to your map. Also, to understand hammer better. Make a map for CS first instead. It's much easier to follow along with tutorial videos. Insurgency isn't the best game to make your first map for.

For guides,
Kliksphilip (My fav youtuber out there)
https://www.youtube.com/playlist?list=PLfwtcDG7LpxF7-uH_P9La76dgCMC_lfk3
https://www.youtube.com/playlist?list=PLfwtcDG7LpxG5QsLnW8FnuQXIVcIOOG0Y

Wafflehoogland (His guides are very clear and instructive)
https://www.youtube.com/playlist?list=PL-454Fe3dQH1L38FnKkz_O1CqYx6sKaXk

If you really want to do insurgency maps, here's one of the few video guides i've found.
https://www.youtube.com/watch?v=aWbSb0-xVTM

The hammer editor is the same for everygame, so you can jump from csgo to insurgency mapping no problem since it shares the same programming, with the exception that skins and models differ per game.

Also
https://forums.newworldinteractive.com/thread-4356-post-37678.html#pid37678

If you want to follow my roadmap on mapping a map for this mod. Not usefull for you as of yet, but in the future it will be the more I update it.